My questions are:
→ Am I wrong to tell him to get out of the trading life in this situation?
→Am I asking for something unreasonable, or is this actually a serious red flag?
Honest and realistic opinions would really help.
You are doing what is right, nothing can change that. But know this, your need for a honest and realistic opinion is why I say this, I wouldn't ordinarily, I feel your pain and genuity. I sensed more than addition while reading your post, entrapments like this are mostly viewed psychologically, but it could be beyond it.
I don't know if you believe in spirituality, that is what I sensed. Trading can be addictive, but the addition is not like that of gambling, it only lasts for a short while after the market had taught you a bitter lesson. Your uncle is entrapped in it, nothing will stop him, if you like feel pity or advice him forever, he will not change. My one and only advice is to go for a deliverance, after which, he should see a therapist or a counselor. Don't overlook this advice.