He definitely will be able to eventually! Try not to worry.
We had physio for my daughter from about 15 months I think. She never crawled (she was a bum shuffler), but she did everything in a rush together. From memory she started walking with us holding both hands at 18 months, pulling to stand at about 19 months, then walking holding on to one hand and then just a finger at about the same time. Within a couple of weeks she was standing unaided. She started to walk unaided at 20 months.
She has continued to be behind on most gross motor skills (took a long time to go upstairs foot over foot, rather than always leading with the same foot, and even longer to go down foot over foot), but she got there eventually. Now at 4 she is still a bit behind most of her peers on gross motor, but she is learning to swim, scoots VERY fast, climbs up things and jumps off them, has just learned to ride a pedal bike, etc. So she's really doing OK. She still doesn't really like crawling 
.
I think what made a difference for her was taking her to Gymboree and just encouraging her (even pushing her) to try physical things a bit outside her comfort zone (but that we knew she could do). We've also just really encouraged anything physical that she did like to do (balancing, dancing, anything even slightly physical that we could encourage and build on). That built her confidence and her muscles, so now she can do most things (though I'd say she is still physically cautious ... but I think her proprioception is pretty rubbish too, which she got from me, so it will be a mixture of factors).
If I remember right the first exercises we started doing with her with physio were just encouraging her to reach out of her centre of gravity - so just hold a toy that he wants slightly further away so he has to lean forwards or sideways a little bit to reach it. Then after time we would put toys slightly under the coffee table so she had to reach under to get them, that kind of thing. We also got a blow up cow thing that she could sit on - which is just slightly unstable so it helps with their core strength, and it also started to give her the feeling of bearing a tiny bit of weight through her legs. Slowly slowly it just builds their core strength up and gets them used to weight bearing until they have the stability to be able to hit all the gross motor milestones. Because their joints are looser, they just need to develop stronger muscles to do all that stuff (whereas kids with hypermobility often also seem to have lower muscle tone, which is annoying).
He will definitely get there eventually - it just takes time and patience!