Employer can seek extension if you do not wish to travel

Overstay cancels the visa. Ideally one should seek a new visa.

Upon filing of I-140, it will interfere with any non immigrant visa.

AOS can be filed when maintaining status for employment-based immigrant petition. Accordingly it can be denied for that reason.

If you change employers now in September, consider if the old employer will have you back on Oct 1 or this new employer will petition?

Day 1 CPT is not favored by Consulates so consider this when seeking F-1

No, it does not apply for consular process

No, you should be fine unless you were driving under influence.

Strategy questions are not the best for online Q&A as personal factors should be considered. What works for one may not work for the other.

If you use your EAD, you do not maintain H-1B. However to prove the lines are blurred. To evidence, use of advance parole is good.