Here's a quick bit of advice from a pro kickboxer on the K1 circuit. I would suggest wearing 10oz plus gloves on the bag rather than bag gloves. The weight is more appropriate both to fitness and fight sport reality. Also will give more cushioning to protect from impact.
But the root cause of your problem may be incorrect punching. The stesses that you are describing are possibly from too much lateral movement on impact, meaning that your body is not in correct alignment. At the point of impact you should have no movement anywhere in your body except through the target - the whole body behind the strike.
It will be worth you getting with an experienced striking coach, and checking your technique all the way through.
Get appropriate medical attention, such as a chiropractor to re-align any bones, working together with a physio to repair the soft tissue. Then, build up the contact slowly, giving yourself a chance to recover from the injury, while also learning the new way of throwing the adjusted techniques.
I've also seen a version of the padded knuckles wrist supports, and I think that they are a great idea and great product.
Good luck with it!
Gary 'Smiler' Turner