50g carb a day might put you in ketosis, or it might not. It wouldn't do it for me - I come out at around 40g/day.
If you're going to aim for ketosis, you'll need some way of checking. You can either use a meter with keto strips, which is the expensive route, or the peestix. The peestix are by no means accurate but they will (in my experience) indicate if there are ketones and give a rough idea of the concentration. I think that's probably good enough for these purposes.
Losing 2kg is not to be sniffed at. I didn't lose a great deal of weight until long after my BG was back in normal range. Most people report substantial weight loss while in ketosis. It's also (in my experience) not a steady loss - it plateaued frequently and then restarted for no discernible reason.
I sympathise with the pain. I don't think mine is related to either diabetes or ketosis, in fact I'm sure it's not. I take naproxen as needed and that has no impact on my BG that I can see. Codeine doesn't either. If you don't manage the pain you'll find it much harder to manage anything else.
Best of luck.