Hi and welcome to JA. Ray here to help you today.
Let's go through these
He had an unhonorable discharge from the military. Not dishonorable. We were married from Nov. 1989 to April 1, 2000. Am I entitled to any benefits now that he is deceased?
Yes you should contact the VA here and see what all they can offer you here.Divorced spouses have rights to VA benefits.
Number 2. He negotiated for the entitlement of my Thrift Savings Plan with the federal government, which reduced the amount I received.
That may go up if he was getting part of your check here, again you have to check with the plan and have it paid to you now.
Number 3. He was receiving approximately $200 a month of my social security. Now that he is deceased, will that $200 come back to me?
Yes it should , if social security was redirecting this then you need to contact them so that you get it all. If you were married for 10 years or more you also may get spousal benefits if his amount was more than you are getting off your wages.
If the Veterans Administration disperse insurance money, do I get a portion or is that just for his children, both of which are adults
Life insurance is payable to his named beneficiaries, if he named you then you would get some or all of it.Check with VA on that too.