Clever how you conflate the existence of the Devanagari lipi to the existence of Sanskrit !!! You should know, if you are a researcher, that the earliest known inscription in Sanskrit is actually written in the Kharoshti script - one of the Ashokan edicts in western India, dated to around 150 AD. The use of Devanagari to write Sanskrit is very much a later practice.
As regards the term Aryan, if again you are a researcher, you would by now have become aware that there was no one Race or one wave of incursion by migrants from across the Hindukush but several groups like the Kushans, the Huns, the Pahlavis and others who came over several centuries. It is no surprise that the term is used not as a noun but as an adjective in the Rig Veda, because there was no one so-called Aryan race as such.
Glad to find that you have discovered that Hinduism is not a religion, and also that you have discovered the six religions predominant in South India whose practices, creed and beliefs have been appropriated and blended with several alien elements to construct the Vedic Brahminism which is now projected as THE religion of our country. Please proceed along these lines and you may find surprising results emerging.