I’m just so tired, doing everything I possibly can for the little guy

I have a 8 month old cocker spaniel and holy shit the last three weeks have become an absolute nightmare. He’s completely unresponsive to positive reinforcement. A positive is He absolutely loves his crate, won’t make a peep aside from alerting me on his needs. But I just can’t keep him in there for more than 4 hours at a time. I work a full time M-F job from 8-5 and come home at lunch for a 20 minute walk. I’m not sure what I’m doing wrong, it’s just been a nightmare. Consistent eating and chewing on things he know he shouldn’t, if he’s not tethered or crated he pisses and shits wherever he wants. Today I let him from room in my 8x4 bathroom for 4 hours while I was at work and he tore the thing up. Worst part is, I come home and he’s not even excited to se me. But if he sees a stranger 50 yards away he acts like it’s the love of his life. I genuinely think he might be autistic. Anyone have any tips for this stage? Would be very very helpful. Just trying to get through this.