1. Yes you need to show POF even if you are CEC. Either funds in your bank accounts or a job offer which annual income that meets the requirement fund threshold.
2. I believe pay stubs only works as POF if you currently have a job in Ontario. Are you not having any bank account at the moment? You should have some sort of documents (bank statement, letters from bank, gift deeds, liquid saving accounts, etc.) to prove that you have enough required funds available. Ref:
https://www.ontario.ca/page/ontarios-express-entry-human-capital-priorities-stream#section-4
3. You should check the the OINP HCP education requirement here:
https://www.ontario.ca/page/ontarios-express-entry-human-capital-priorities-stream#section-2
2. Education
You must have a Canadian bachelor’s, master’s or PhD degree or its equivalent in another country.
If you completed your studies outside of Canada, you need to obtain an Educational Credential Assessment report that proves your education is equivalent to a Canadian credential.
Someone got their application returned due to having a diploma instead of a degree, I'm no expert, but I would advise you to double check your eligibility before applying ( but if you
also have a degree-equivalent education outside of Canada, and your ECA shows that, then ignore this, you should be good!). Here's the post:
https://www.canadavisa.com/canada-immigration-discussion-board/threads/incomplete-application-oinp.832052/
5. I believe you could change the date on EE as long as it doesn't affect your scores. I did make some minor changes in my spouse's work experience after received NOI, and still got the nomination.