I am looking for any scriptural sources relating to whether Bhakti towards a lover, a king, a country, or a physical idol can lead to Moksha by itself, or does one need to have Bhakti for the formless reality?
If so, how does this Bhakti enable us to realise Brahman?
There is no Bhakti for Formless reality. It is always Jnana that enables one to achieve formless Brahman. This is the definition of Bhakti in case of Nirguna-Upasana:
Among things conducive to Liberation, devotion (Bhakti) holds the supreme place. The seeking after one’s real nature is designated as devotion. Vivekachudamani,32 (Adi Shankaracharya)
Now, No, bhakti towards any physical object or person cannot lead you to Moksha. There is no scriptural evidence for this. This can happen only in case of Saguna-Brahma, that you achieve Moksha through Bhakti. Do not doubt that the Saguna-Brahma has physical appearance too, because when Lord descends as a person, his body is not like ours, it is Chit-Anand-May, that is "consciousness and blissfull".
चिदानन्दमय देह तुम्हारि। बिगत बिकार जान अधिकारि।। Your body is existence-blissfull and without any worldly conjugation, not everyone can know this. (Ramcharitmanas, Ayodhya kand: Tulsidas ji)
The attachment towards material world and people are reason for bondage, it cannot lead to Moksha.
बालस्तावत्क्रीडासक्तः तरुणस्तावत्तरुणीसक्तः । वृद्धस्तावच्चिन्तासक्तः परमे ब्रह्मणि कोऽपि न सक्तः ॥ ७॥ The childhood is lost by attachment to playfulness. Youth is lost by attachment to woman. Old age passes away by thinking over many things. But there is hardly anyone who wants to be lost in parabrahman. (Bhaja Govindam, 7: Adi Shankaracharya)
This shloka clearly states that one needs to give up materialistic thoughts to achieve Brahma.
No, God cant be realized through love towards a lover or something selfish or material thing like Greed, lust or passions, because God is the Supersoul/Spirit and is selfless/egoless but carnal love, lust or passions are physical and born from Ahamkaar/ego.
Ramakrishna Paramhans explained Maya is of two types
Ramakrishna regarded maya to be of two natures, avidya maya and vidya maya. He explained that avidya maya represents dark forces of creation (e.g. sensual desire, selfish actions, evil passions, greed, lust and cruelty), which keep people on lower planes of consciousness. These forces are responsible for human entrapment in the cycle of birth and death, and they must be fought and vanquished. Vidya maya, on the other hand, represents higher forces of creation (e.g. spiritual virtues, selfless action, enlightening qualities, kindness, purity, love, and devotion), which elevate human beings to the higher planes of consciousness
If you must be mad, be it not for the things of the world. Be mad with the love of God
God can be realized through both Bhakti/love or Gyan/intellect. As unmanifested consciousness is called Brahman/Shiva/static reality in Vedas while manifested consciousness is called Maya-Shakti/Vishnu/dynamic reality in Puranas.
“Even after having attained Perfect Knowledge, teachers like Nārada retained love of God in their minds for the welfare of others.”
MASTER: “Bhakti may be likened to a woman who has access to the inner court of a house. Jnāna can go only as far as the outer rooms.”
A DEVOTEE: “Has God a form or is He formless?”
MASTER: “God has form and, again, He is formless. Once upon a time a sannyāsi entered the temple of Jagannath. As he looked at the holy image he debated within himself whether God had a form or was formless. He passed his staff from left to right to feel whether it touched the image. The staff touched nothing. He understood that there was no image before him; he concluded that God was formless. Next he passed the staff from right to left. It touched the image. The sannyāsi understood that God had form. Thus he realized that God has form and, again, is formless.
** “But it is extremely difficult to understand this. Naturally the doubt arises in the mind: if God is formless, how then can He have form? Further, if He has a form, why does He have so many forms?”**
DOCTOR: “God has created all these forms in the world; therefore He Himself has a form. Again, He has created the mind; therefore He is formless. It is possible for God to be everything.”
Personal God and Impersonal Truth
MASTER: “These things do not become clear until one has realized God. He assumes different forms and reveals Himself in different ways for the sake of His devotees
Swami Vivekananda Quotes
God is very merciful to those whom He sees struggling heart and soul for spiritual realization. But remain idle, without any struggle, and you will see that His grace will never come.
Knowledge can only be got in one way, the way of direct experience; there is no other way to know.
Bhakti of formless reality can be done, and is infact done in Sikhism where Brahman is called Waheguru and 10 Sikh Gurus and their followers are proof of that who are protector of Hinduism/Sanatan Dharma in North India.
Waheguru (Punjabi: ਵਾਹਿਗੁਰੂ, translit. vāhigurū) refers to the almighty God, the supreme soul, the creator in Sikhism.
The word vāhegurū is traditionally explained as being composed of vāhe "wondrous", gu "darkness", and ru "light", together said to carry the meaning - The wondrous Lord who dispells the darkness of ignorance and bestows the light of truth, knowledge and enlightenment.
The word Vaheguru or Waheguru is also used in Sikhism as a main mantra, called gurmantra or gur mantar.
