If it won't start for a couple of seconds using starting fluid, it sounds like there is a fuel-related issue.
As far as the Schrader valve, just turn it in until it stops and then gently snug it.
Do me a favor. I want you to recheck spark to the plugs. Follow the directions in this link and let me know what you find:
https://www.2carpros.com/articles/how-to-test-an-ignition-system
Additionally, if you could record it cranking and upload it for me to hear, it may be helpful.
I will watch for your reply.
Joe
Sunday, January 2nd, 2022 AT 8:46 PM