Put the screws back in the box, use glue only, put slots in the MDF and use carr.bolts and knobs..so you can slide them easy..I will suggest a 3 part fence,that's to say, a out feed side a infeed side a insert type in the center, the center one has 10 deg. angles on the ends of it to hold it in place..and match up with the other two part...
I'm building my router table fence now and the angled face pieces are a nice feature. I was planning on more carriage bolts to hold the center insert but this is a much more elegant solution.
I elected to place the t-track above the sliding pieces and fastened to the back plate (behind the slidy pieces) but may reconsider. Placing it above does require a longer featherboard but I wanted to make a few anyway (where's the pattern for that curvy one?).
Why not glue and screws to attach the fence back plate to the base? I'm using a piece of 3/4" melamine for my base and the core wood is more like chip board than MDF. I'm not sure how good a bond joint I would get with just glue.
I also decided to put the slots in the backing plate instead of the MDF sliders. This will make them easier to replace and provide more flat surface for the fence. It should also make them last longer since the bolt heads will have support all the way around the head instead of just on the sides. A large flat washer on the back will distribute the clamp load. Also, the back plate is plywood.
I'm using wooden L-clamps to hold the fence to the table rather than t-track in the top. For now, I've also omited a miter slot in the table but I may add one if, after using the table for a while, I find it's needed.