Wing feathering isn't always accurate, and looking at feathers alone at this age isn't usually accurate either. The hackle and saddle feathers will come later, the large red comb and wattles indicate it's a cockerel, sorry.
You got him from TSC from a bin labeled Wyandotte and another breed but you're not sure what the other was, correct? I don't think lavender Wyandottes are very common but I'm unsure what hatchery the TSC near you would be supplied from!
1. Looks like a silver laced Cochin Cockerel :(
2. I would agree likely a boy, comb is big BUT it's not red yet so maybe if you cross your fingers extra hard!
3. Comb is a little big, keep an eye on this one, may end up being a cockerel
4. Silkies take a lot longer to sex, so can't say...