After reading all the topics you wrote, I am very concerned about the difficult situation you are facing. It seems that your uncle has fallen too far into the trading addiction zone which makes it difficult for him to think clearly and make good decisions.
→ Am I wrong to tell him to get out of the trading life in this situation?
You are not wrong at all, trading is not a stable job and can cause huge losses if not done properly. It is very important to take action to stop your uncle before he gets caught in a worse situation because all this time his activities have shown signs of addiction, especially since he has suffered huge losses.
→Am I asking for something unreasonable, or is this actually a serious red flag?
You're not asking for anything unreasonable. I fully understand and appreciate your good intentions in wanting your uncle to have a stable and prosperous life. This is perfectly reasonable, as you want him to change his life direction to have a stable income and not rely on trading, which has caused him significant losses.
Continue to support your uncle by encouraging him to do something positive so that he realizes that all this time his actions have been problematic and he needs help. If he still persists in his actions without paying attention to your advice, then you should keep your distance from him, this action does not mean that you no longer care about him, but to protect you from an unhealthy situation.