You mentioned a prescription card, I didn't know if it was PC's or another one. It has saved quite a lot in the past and can check ahead of time with the pharmancy how much the med will be with it before getting it filled to know how it will help, as it can go up to 80% but not all meds are at this discount. Here is the link to download PC's which might help if not already familiar with it:

Announcing the Psych Central Drug Discount Card | World of Psychology

It can also be helpful to contact/look up the manufacturer; many times they will have a program to help pay for their meds at a reduced cost for those w/o insurance or evenr ebates for those with insurance sometimes, which the pricing is at a fraction of the cost otherwise.

Be sure also to contact all the pharmacies in your area to find the lowest price; sometimes it is surprising the differences between them to get a better rate, especially Walmart is known for this.

Also talking to your doctor to let him know your concerns and see about free samples to start.

I know these are hard decisions you are having to make and will be sending good vibes your way to find a solution and that the right med is found sooner than later that is affordable. Hang in there and wishing you and your son all the best.