Potty training disaster

Hello I am trying to figure out what to do. We are trying to potty train my autistic 4yr old, basically it’s going badly. He is pooping on the floor, carpet, couch etc. he is sitting on the potty every 25mins for 5-7mins. But when he gets off then he goes and poops. I don’t know what to do. On one hand I don’t think he will ever understand that the potty is where he goes and I don’t know how much more floor poop I can clean off the rugs and carpets. I am not sure if to just give up and try again in a year but he’s already 4. Help lol