(ANY ADVICE) Garter snake seizures and not been eating for a few weeks.

I'm an expat living in China. I have a red sided garter who is around 6 months old.
Recently it's been having severe seizures and has not been eating food. (Due to me only feeding it fish and realizing too late)
There are no vets or services near me that could really help with this situation.
I did try taking it to my local vet who owns some reptiles, and they were able to administer some vitamin B and it helped abit.
They gave me a supply and showed me how to administer it. I force feed the snake (with varies diet + pinkies) with the vitamin B and I've noticed he's calmed down slightly. But he still has seizures on a daily basis.

I'm lost, do I keep force feeding him while adding the vitamin B supplement?
Am I too late?
I have to use a VPN just to get on this site as there is no information on Chinese internet that can help.
With all this madness with forced lockdowns and zero covid policy stuff it's really affecting me, and I feel like I may lose my snake.
I don't want to lose him but I don't want him to suffer so much.
What can I do?
Any advice and knowledge would be helpful.
Please and Thank you.