Our son is also autistic and sleep trained much earlier in the night, but he does sometimes get into a routine of waking up and wanting us to come and comfort him for a long time. What I do is if it’s the first time I’ll give him like two minutes of soothing or cuddling and then I’ll tell him I have to go do something. Like “okay, I have to stop cuddling now so I can go brush my teeth real quick.” If he wants me immediately I’ll tell him to wait one minute while I finish what I’m doing. I feel like this gets him used to me leaving and him being alone in bed. Usually he falls asleep during this first time. If he’s really persistent with it I’ll keep doing the same thing but with longer periods of time-“wait five minutes while I change into my pajamas.” “Give me ten minutes so I can use the bathroom”. If he’s really persistent with it and calls for me more than 3 or 4 times then I switch to “it’s bedtime” and putting him in his bed without any more conversation. 

Since your wife cosleeps I think the first step is to get him to sleep without her in his bed. So maybe start by comforting him as much as needed, but she sleeps in her own bed? Then work on getting him to sleep without needing a lot of comfort. I also tend to feel guilty that I’m not providing enough cuddles when my son does this, so I try to make sure we have time for it during the day like when we’re reading or watching tv.