Welll, not knowing your set up, I'd likely start with making the 3.5 gate higher and applying plywood if he's getting legs through. Then I'd look at how to make an in/out situation for the horse...
Bulk shavings here- delivered and put in the barn. Very clean softwood shavings. Same quality as the baled shavings we get around here but one/quarter the cost. You just have to find a supplier with...
I have borrowed an old gelding in the past to keep a youngster company . It's usually not necessary to buy companion horses. Free room and board for the time needed benefits all.:)
If you have people in your barn who are brazen enough to take a crowbar to the tack trunks, they are brazen enough to choose the right moment to just walk out with your brand new taCK box, regardless...