I paid a lawyer $5,200 sons divorce. . Not much here 2 vehicles 23yr old motorcycle. $18,000. Going for pretrial March. Now wants $7,500 Maybe a trial

Son is SSI disability. Wife a registered nurse. Mediation went no where. Wife's mother is rich. Pre trial in March. IF IT GOES TO TRIAL LAWYER WANTS $7,500 MORE. He said it will take up many, many hours of work. I can only pay in monthly installments I live on small pension and SSI. Lawyer said to make out 13 checks payable to him on the 15th of the next 13 months and send it to him. I do not understand. There just doesn't seem to be any huge amounts of assets in marital property. Maybe this will be settled in pre trial or if his wife's lawyers make a decent offer. Why should I send him the 13 checks for $600 now? Is there some one that could take over this case, because my son has no money after paying for living expenses. $7500 more for so little in marital property for a trial. The joint custody for two children is already settled. He has us over a barrel. If I do not come up with money, I do not think he will fight very hard for maintenance issue. I just do not understand, HELP