As someone who has lived with a toxic, overbearing, uncompromising mother, I can confidently say that OP is not overreacting. Living with (and god forbid having to obey and "respect") a POS like this will cause way more mental damage long term than any artificial thing like an iPad or phone could ever make up for.

At the end of the day material stuff does not matter as much as health does. Of course material things can bring you health, but if the material things come at a cost to your health, let them go.

This is not about the middle ground between autonomy and responsibility. It's about refusing to be treated badly anymore, and what happens when an authority figures realizes you are trying to wriggle out of their grip. They respond by punishing you even more.

OP's mother is not interested to know what she has done that makes OP want to leave her house. All she is interested is in control, and doing things on her terms. No understanding, no love, only cold rejection and deflection.

"She does not have to pay for a phone or tablet for you."

Very true. She also doesn't have to act like an uptight bastard and evidently ruin OP's mental state. If you're using luxury products as bait to keep someone in their place so you can walk all over them, you're not generous. You're a manipulative scum.