@ghost_whistler - You do seem to be going through it at the moment. I feel for you.
When you see your GP, please do make sure you ask him/her for more test strips, so that you can track what is going on. That really will be a major tool in unpicking your puzzle. Do you keep a diary of what you are eating, and alongside it you blood scores before and after eating that meal/snack? That could really start giving your personalised feedback that could help inform you, and also make any future medical appointments grittier, in that there is real, personal, up to date data to be examined and discussed.
As far as your most recent doctor describing your condition as a 'very reactive metabolism', that's not a million miles away from how I, personally, might explain reactive hypoglycaemia in the simplest terms. I don't suffer with RH, but have read quite a bit about it, having been around these parts for a while now.
In order to understand things, I'm one of those people who likes to visualise things. My way of visualising RH is to imagine someone juggling. Nothing special. No flaming hoops or knives, just maybe three tennis balls. It takes concentration, and attention to detail, but it isn't dangerous. That balls go up, reach their peak, then they come down, at a steady rate, they're caught and it all happens again. In the end it's just a routine. That's a normal metabolism.
Where someone has RH, they can do some juggling, and whilst the do it in nice calm conditions, where the conditions allow them to rhythmically recycle those balls, they do fine, but if they juggle under a low ceiling, the balls, rather than just stop climbing, then drop in the usual, controlled way, they bounce off the ceiling and come down a bit fast. When they come down that fast, it catches us off guard and we can't react quickly enough to catch them, so they fall to the floor. That's how I see it.
In that circumstance, the person has to adjust how far up they throw the ball, so that they have the skill to catch it on the way back down. That's exactly how trimming back the carbs works for RH. If the bloods don't do up with much oooomph, they won't rocket back down again.
My personal thoughts (not bourne out of personal experience) are that that ceiling will be personal to each RH sufferer. If there was a magic blood number that shouldn't be breached, the solution would be simpler.
My thoughts on your next steps would be to test, test, test, and keep records. The records should track intake of food, your blood testing and anything else "special", like heavy exercise or illness/colds; that sort of thing. You may then be able to see patterns for yourself.
Take it steady of the thought of going hard keto is too extreme for you in the first instance.
My feelings, however, would be that, if you have RH, you are much less likely to have crashes is you have reduced the carbs; provided you don't go from making sandwiched from bread to making them with two steaks and a chicken breast between!
Yes, carb/keto flu exists, but usually only for a couple of days - for those who experience it. It strikes me that you've been going through the mill for some time, and without some action things are unlikely to change. A change bringing discomfort for a few days could be a real investment in time.
Take it steady, maybe for you cut back, rather than cut out is the way forward.