The best way to contact most Thai embassies is through Facebook messenger. Find the embassy on Facebook and send a single, precise message so they do not get confused. Name, application number, passport number, and question, all in a single message.
Do you have a very bad entry history for Thailand? 8000 is usually for people that have already been denied entry or have a very checkered history. If you don't have that, I would check with some other providers first.
Generally the "sponsor letter" is for those applying for a dependant DTV based on someone who already received their DTV. The primary person can sponsor their spouse and children rather than show money in their accounts.
The only other reports I've seen related to sponsor letters were from direct family members, but even then I've seen reports of it being denied.
there is no rule about 2 entries. There used to be a rule about 2 entries per year at a land border without a visa, but that rule was abolished when visa exempt went to 60 days.
It's probably fine. It's more about how long you've been in Thailand than how many times you enter. You'll only have been in Thailand for 2 months. Just make sure you have all of the required items when you attempt to enter.
1) Proof of funds (20,000 baht or equivalent in another major currency IN CASH ONLY)
2) Proof of onward travel (a ticket leaving Thailand within 60 days of your arrival
3) Proof of lodging (at least a couple of days hotel reservation from the day you arrive)
Every immigration office has different requirements. Generally you'll need a copy of your TM30, your entry stamp and visa, and whatever else the immigration office might request.