Jeez, kel! I'm not stalking you, this post just came up on Active Convos so I had a look and of course recognised your name. No wonder you have such a shit time with men with a mother like that...
No, it's not right, it's not right at all. In the long term, I'd be looking at moving house, even if it meant changing jobs. You need to get away from her. In the short term, you're unlikely to get your key back from your mum so get the lock changed. If you have a Yale type lock, it's easy and inexpensive to change the barrel, you need a screwdriver and about a fiver. And fit an internal bolt.
You take the phone, the ipod and all other techy stuff off your ds. At 11 he's at the start of the "getting arsey" stage (aka puberty) and if you don't sit on his head hard asap you'll have an absolute fucking nightmare in a couple of years' time.
If ds "needs" an ipod to do his homework, he does it in the same room as you, with you checking what he's doing every five minutes. You remove the ipod as soon as he's done. Switch off the wifi/change the passcode so he doesn't have it; do this daily, he gets no online time until the homework (and other chores of your choice) is done.
You really need to set down your boundaries with your mum and your ds, and hold hard to them. It won't be easy, but there's no alternative now.