Guess what? I think you are worrying over nothing.
Every child does things at their own pace, and here is the clincher, if he wasn't happy doing it, he wouldn't do it.
Babies and toddlers have more inteligence than we give them credit for.
My eldest and my youngest both couldn't wait to get upwardly mobile, whereas my middle one was so laid back about it all we wondered if she had weak legs or something.
Result? nothing of the kind, she just wasn't ready, and all 3 have had nothing but a cold very rarely, and all have grown up fit, healthy, and full of life, and please God, so will Rem.
Remington is most likely fine and will almost definitely be just fine developmentally even if he never crawls. My cousin and i both went straight from laying around to walking without much crawling beforehand, but according to my mom i decided i'd rather crawl.
Raine used to absolutely hate tummy time, but we kept doing it and when she was three months exactly she rolled over. After that i decided to do more tummy time no matter what. So now we have a special tummy time blanket that has interesting patterns on it, and i lay down a couple toys - her bunny head blankie thingy and a dog rattle thats black, white, and red and she tries too get them. She is 17 weeks and scoots around now thanks to the toys because she really wants to eat them :D I hope he learns to like his tummy time...
Oh and they make tummy time mats to help make tummy time more interesting for babies, and with the way he likes his little bouncy seat thing (which is probably why his little legs are so strong) he'd probably like them just because it's bright and has toys and stuff.