How long has he been in your home again?
I think you are trucking along pretty good. He likes you is interested in you he wants to. It really just does take longer than you have , to build trust and confidence. Especially as I'm sure he has some hiccups with the young child in his previous home. Because if he was at love bug stage they would have kept him.
In my head he started out well socialized by breeder and a sweet baby, then not enough time with him every day, and some hesitancy and nips and jerking hands away..but he was rehomed before he became completely fearful and out right attacking. So a little confusion, and hesitation.
If he has got treats down like this , then just start working a little harder for them. Coming to you, moving him around out of cage perches coming to you for treats . I would put a rope perch across the length of top of cage. So he can move easier and with confidence. Then have him walk to you from far side for treat. Then go to the other side and have him walk the length again for a treat. Once he has that down. Id lay a hand flat on top of cage , and have him walk on rope over hand from one side to the other. Then I'd have my hand on rope flat sort of mashing the rope flat in that section and have him walk on rope then over hand on rope to get treats . Some variation of thst till walking over your hand was no big deal. Then trying for pause in hand as walked over .
Or /and other simple things to get treats, touch this for treat, the turn around for treat . They can pick up little stuff like that pretty quick. Especially now that he is addicted to crack safflower seeds!