Been on Reta for 22 weeks and the last few weeks weight loss has stalled big time and appetite has come back especially at night, am down 47 kg , was on 15 mg a week but bumped it up to 20 mg a week and no difference !!!!
Given where you started and the loss of 47 kilos, the reta has worked a bit less well than average, but not much, so about 25% loss rather than 29% plus that is the average from 12mg of reta over a year. Higher doses of reta have never been studied in humans yet so it is hard to say what to expect from doses higher than 12mg, on average you would expect some extra weight loss, but you are getting into diminishing returns territory where higher doses will not cause much extra weight loss, but might cause worse side effects.
The important thing to realise is that it is still working and stopping you from putting the weight back on, Even if getting to 150kg from 200 is less than you hoped it is still enough to make a lot of difference to long term health, and keeping it off is as important as anything.
But I would second adding in elora ( or cagri ) , no good human studies yet apart from semaglutide with cagrilintide. Cagri is probably a bit less effective and has more side effects than elora but is cheaper . Elora has literally only been available for a few weeks. There are very good reasons to believe you could get a fair bit of extra weight loss out of reta plus cagri or reta plus elora. And much more likely to work than increasing reta more or adding in tirz. But starting at very low doses of cagri is important 0.25mg and increase slowly, or if elora maybe 1mg and also go slow. The way I see it is the adverse effects of combos of GLP drugs are mostly unknown, but given how severe the health risks are of severe obesity it is very unlikely they are worse.
I think a fair bit of the advice above is not taking into account the issues of hitting the gym at 150 kg plus, if you can great, but if not, waiting till weight gets down a bit more might be more practical and safer. I know I could not even start walking much till I got down from 145 kg to 115kg and even then a 5 minute walk was really quite painful. But from there I was able to gradually build it up.
The 1000 kcal/day is not impossible in the context of long term low calorie metabolic adaptation, but even then is pretty low for that weight. It might be worth trying to get a more precise estimate by weighing everything you eat and writing it down for a week and I found chatgpt was pretty good at calculating calories / protein / carbs etc from the foods and amounts, or even a professional dietitian appointment might not hurt.