You really have the worst possible situation there with Magoo and the other kitties - I’m so sorry!! Because of Magoo's sad past, it will probably take quite a while before he can relax and trust anyone, both humans and kitties.

Having followed this since you took him home, I honestly think the best for all parts would be if you could find him an only cat home. Or if he could live in an outdoor enclosure where he's safe.

You have gone to such lenghts to try and help him and I admire you for doing do! In your shoes, I'd give it another few weeks, the most.

Poor Magoo, you and your kitties!

{{{{Hugs}}}}