To conclusively answer this, you need to understand sanatan dharma (hinduism as they call it) from 2 lenses i.e Shruti and Smriti. Shruti as you would know means that which is heard or that which was communicated from the beginning. Basically, shruti means the reality. Our 4 vedas fall under the Shruti category and hence are irrefutable because it is wisdom which has been dictated by god himself and so it is not man made. Smriti is that which is remembered. This is the category of katha or scriptures that were man made. Upanishads which are commentaries on vedas would also fall under Smriti category because it is man made and are opinions of men on vedas.
I , for one, partially agree with Swami Dayanand's Saraswati vision that vedas are the absolute truth. You see, our smriti's have been adulterated over the years by vested interests. So if you manage to get a copy of Ramayan or for that matter any puran say 100 years back, you would know what i mean. You would definitely see added sholkas which were not there in the original copy. And it is this adulteration that has damaged Hinduism and this was the view point of Swami Dayanand Saraswati. So for e.g Sati pratha, meat consumption etc...are all examples of this adulteration. Even if you compare Tulsidas Ramayan and Valmiki Ramayan you will be shocked to see that Tulsidas Ramayan has substantially deviated from the original story line. In fact, the whole of Uttar kaand (last chapter where after the war Lord Rama send mother Sita to forest again) is an example of such adulteration. The whole Uttar kaand never happened. So on this front I'm with Swami Dayanand saraswati ji because this damage has changed our beliefs, our notions. We find ourselves constantly defending actions which we ourselves are not convinced about. This whole dhobi episode in UTtar kaand. There has been so many debates on it. But is this really part of Ramayan ? Did it actually happen ? Lord Hanuman was a learned yogi ..knower of all vedas. Can a monkey do that ? Did he really fly ? Did he actually swallow the sun ? these are the adulterations i'm talking about. The laws of nature that are existing today were the same laws that were existing then. Why would god defy his own laws ...his own rules...what kind of precedence will he set for others imbibe by that...these are the valid questions that you need to ask. FAct of the matter is these are damage done to the original story over years of abuse by people in power. And it is easy to figure out these adulterations. All you have to do is read carefully. Any 2 shlokas should have some continuous context and if the context suddenly changes you know that it was added later on. An example in Manusmriti...Khand 5 shlok 10---kind of food that can be eaten...the shloka in sanskrit says....you can eat vegetables and grains etc.....and in shloka 24 it says that you can eat these vegetables and grains in the morning..only if they have ghee in it.....so you see shlok 10 and shlok 24 are connected ..they have the same context...but how come all of a sudden ..shlokas 11 to 23 ..suddenly started talking abt eating meat. You know for sure that this was added later on. That's how you zero in on adulterations.
coming back to your question...teachings of Dayanand Saraswati and how it conforms to what Vedas teach...Dayanand saraswati outrightly rejected Smriti's (which means Ramayan, Mahabharat, Upanishad) etc because of these very adulterations that I just spoke about. And because Vedas are pure knowledge based on science and logic it was difficult to mess around with Vedas and in that sense Vedas is more authoritative and the fact that it is also not man-made . Smriti's were easier to mess around with because these were man-made interpretations or stories and it was easy add something in between the stories. Hence Dayanand Saraswati rejected the notion of Smriti's.
However, this is where I deviate from Dayanand Saraswati's philosophy. While i agree that yes there are adulterations...and the context has been messed around with...i, for one, believe that Smriti's also give us wisdom and in that sense are also part of Vedas since vedas literally means wisdom. We should not forget that Mahabharat is a Smriti which has the best shruti in the form of Bhagwad Geeta since Geeta is not man made.
Going by Swami Dayanand's Saraswati vision idol worship is a big crime since it is not advocated anywhere in our scriptures not vedas..not smritis.....and this is where your questions are valid...but the vedas itself has the answer here.
God is experienced in two aspects – as Nirakar and Sakar.
Verses Describing God as Formless (Nirakar)
“Na tasya pratima asti”
“There is no likeness of Him.”
[Svetasvatara Upanishad 4:19, Yajurveda 32:3]
God says: “You cannot see me with your present eyes. Therefore I give you divine eyes so that you can behold my mystic opulence” (Bhagavad-Gita 11.8)
“He is body less (Here Body means the physical structure, including the bones, flesh, and organ. Brahman has unique transcendental formless spirit body which is infinite like space) & pure.” (Yajurveda 40:8)
God as Nirakar Nirguna Brahman or Supreme Consciousness is body less and pure. That doesn’t mean His Sakar Saguna form is impure, it is pure too.
Verses Describing God with Form (Sakar Saguna)
“The Lord of the universe, Lives inside the universe, And without being born, Appears in many forms, And only the wise realize his real form” - (Rig Veda Purusha Suktam 2.3)
Whenever & wherever there is a decline in Dharma/righteousness & religious practice, O descendant of Bharata, and a predominant rise of irreligion-at that time I descend (Sruja-send myself forth/Descend/take visible form) myself (aham-I/Me, atmanam-self). (Bhagavad Gita 4:7)
Though unborn, it appears to be born in diverse ways. (Yajurveda 31.19)
Therefore it can be understood now that God has two forms Nirakar Nirguna & Sakar Saguna. These two form Characteristics of God like all-powerful, all-knowing, all-merciful, pure, infinite etc. remains the same. Just like water has three forms – liquid, solid & vapor, though it appears in different forms the core substance H2O remains the same in all forms. In the same way, the Brahman/God is one without second & has the ability to manifests in different forms at the same time anywhere on the earth & still remaining present everywhere. Its formless feature is omnipresent & infinite like space and it is able to manifest in many numbers of forms at different places at the same time without ceasing the existence of its ultimate omnipresent nature
So the above basically understood in the following way
God exists in 3 forms simulataneously
1. Parmaatma/Parbrahma or Brahma Kaaya- Absolute Impersonal Form (Nirakaar/Nirguna)
2. Celestial personal form or Divya Kaaya - Brahma, Vishnu, Shiva, shakti (Sakaar/Sagun) but with body of pure bliss and clear light emanation of absoulute spirt ie Parmaatma
3. Avtaars (Lord Ram/Krishn) or Manushya Kaaya - body which manifests in space and time
Ony Brahma Kaaya is absolute reality . Divya Kaaya and MAnushya Kaaya are provisional ways of talking about and apprehending it.
In bhagwad Gita, Shri Krishna declares that those who are attached to the unmanifested, impersonal (formless, infinite, space-like, transcendental) aspect of the Krishna, for them the spiritual advancement is very troublesome. To make progress in that discipline is always difficult for those who are embodied. Some of Abrahamic religion worship Supreme reality in formless feature so according to Shri Krishna for them, spiritual growth is slow and tough. Shri Krishna prefers worship of Supreme reality in his divine personal form.
What that means for us is that we as species who understand sakaar and saguna, the provisional ways of understanding the Parmaatma will help expedite our spiritual growth and in that sense Hinduism is far more rich and diverse when compared to Abrahamic faiths.
Hope this helps