There are lot of persons here who are masters of vedas and will give you an excellent answer. I am not as muchas experienced to them but will give an answer to my knowledge.
Here you have asked a question about a specific purana in Hinduism named Garuda Purana, First you should understand that Vedas or any other purana is not an absolute rule to be obeyed. It just says the best practice of meeting the god
1. Vedas says about cleanliness of one inside a temple and says about the food to be offered to the god
But it does not mean God will not accept anything other than that. See the image below he is Kannapa Nayanar. He keeps the leg on the eyes of lord shiva and meat is offered to him. He does not care.
There is also a similar story in Ramayana - Sabari offers half eaten fruits with lord rama.
So, from here you can realize that God will accept anything which has love.
2. Why God is creating fear in humans in the name of punishments?
God will do anything to save you from suffering, Literally Anything! here is an example God consumes poison.
This has created an everlasting stain on the neck of Lord Shiva, why does he do that? Just to save you(everyone) and me from suffering. It is ultimately us who choose the wrong path and end up in the wrong place(hell). So remember god does not hold the key to hell, it is with us to choose the right path.
There is a similar statement in Bhavat Gita to prove this,
BG 9.25: Worshippers of the celestial gods take birth amongst the celestial gods, worshippers of the ancestors go to the ancestors, worshippers of ghosts take birth amongst such beings, and my devotees come to me alone
credits: Uday Krishna for providing verse number and completing the statement.