Try not to worry, it will get better.
We are just coming out the other side with DS2 at 14 months.
He was always a sicky baby but once we started weaning it was a nightmare. He gagged so easily on anything. I have posted on her a few times about him.
We were referred to a feeding advisor who as someone else mentioned said to try the bite and dissolve food. Things like rusks, cakes, chocolate buttons broken up, cheerios, quavers, wafers.
The feeding advisor suggested trying these foods then trying more chewy stuff again. TBH we still aren't completely there but he is rarely sick now. He still has a soft diet and won't eat pieces of meat, fruit or veg. Apart from strawberries.
I got really stressed with it too. He was a skinny little thing but weight never dropped enough for them to be concerned. The last month or so since he had been eating better I can see his cheeks filling out.
Although today a friend gave him some flapjack and he vommed everywhere. Its amazing how calm you become about it!
Oh and I've used more jars this time round as DS2 seems to tolerate them better.
Also I think the chewing theory is overrated. DS2 doesn't talk yet but has always made loads of different sounds. But thats just me!
Take care.