Bad Contractor and my rookie mistake! Need advice

[Caleb Scott]

Hey guys, so here is my situation. Here in San Antonio i  purchased a flip as a bank owned foreclosure. I am using a general contractor because this only my 2nd flip and i'm not comfortable taking on the full project myself yet plus its a huge project (Historical district 1931 built 3/1) the contract between the GC and I is for roughly 70K and was to be paid in 3 installments with the last one upon completion of the project. We went under contract wit the first installment paid and about 2 weeks later he asked for an early partial second installment "to keep the project funded and moving smoothly" I was hesitant but i went ahead and did it. since then, he has left my roof open (improperly tarped)  while replacing it during the recent downpours we have had and we had quite a bit of water come in the house. We were able to get big fans going and dry everything out but what he forgot to do was remove all the wet insulation in the attic which sat for about a week untill I myself spent two days removing it all. While doing this i noticed what looks to me like some small black mold spores beginning to grow. I took everything out, washed the mold spots with bleach water and sprayed with special mold killer and informed my contractor of everything and requested that a mold inspection be done to be sure that it was all taken care of. Word got out to his employees and they now refuse to work in the house bc of the black mold accusation and he is blaming me saying that the project didn't need to be stopped and i shouldn't be making accusations that there is black mold when he believes it is just algae. either way.. i want an inspection because i know i have to disclose all this when i sell and want to cover myself and obviously give the buyer a mold free home. Long story short there have been 3 or 4 other instances that were totally unacceptable during the job and i really would like to fire him but i am not sure how to go about it! also, i should have never paid him the second installment which puts me at about 40k with him and there has MAYBE only been about 15-20K in actual work completed by him. so do i ask for an agreement on the cost of work that has been done and ask for a certain amount of money back so we don't Have to go to court? or is court my only option? or am i stuck since i already overpaid him? thanks for any advice and recommendations for good residential flip GC's in san antonio as well as somebody who can give me the best legal advice! thank you!!!