You can not pre sign all the documents, the copies of ID card and house papers from wife should be signed by her, the copies of marriage certificate and kor ror 2 by both.
You applied for an annual Extension of Stay a couple of weeks later than arriving in the first week of may. Did the Immigration Office made the 90 day report, to get you into sync with your annual application. Check the dates as a few weeks after arriving somewhere beginning may could be less than the 75 days to report 15 days ahead.
As long as you wait for your Work Permit you can not get any Extension of Stay based on Employment. Talk to the Ministry of Labor and ask them why it take so long.
By the way, working without this Work Permit is officially not allowed, be careful.
Yes, when the visa expires and you still have a period of stay or you apply for the 1 year Extension of Stay you need a re-entry permit, single cost 1.000 Thb multiple cost 3.800 thb and these will give you the same last date as permitted to stay on entry.
I guess you apply for this visa based on being married to a Thai National.
1. yes and be aware that after 60 days you can apply for a 1 year Extension of Stay but than the minimum of 400.000 Thb needs to be at least 2 months on that account.
2. yes
3. Yes, you need an address as the Immigration is going to visit that address to see if your marriage is de jure and de facto.