Ruby, let me make a couple of assumptions. Most reso's have flat tops. The most common cone well depth for a biscuit guitar is one inch, that will put the top of the biscuit itself about 5/16 above the plane of the top. Radius your biscuit to match your fretboard and cut string grooves like you would an nut - maybe slightly deeper. Now adjust your neck angle by shimming the stick until you have approximately the action you want (will vary depending on your ratio of slide to fretted). You can make minor tweaks to the action by filing the slots a little deeper but most of it comes from the stick.
That should clear most commercial cover plates but I always advise getting cover plate, cone and biscuit before your start and doing a mock up of neck angle to make sure.
You can remove material from either side. The biscuits that I have purchased have the saddle glued in so its a moot point. Cone compression has been negligible in my case.
Thats actually a carbon fiber biscuit - pretty expensive and I couldn't tell any advantage. The NRP Hot Rod cone was a definite improvement over the stock one - if you haven't bought your cone I recommend that one. The tailpiece should have a piece of leather or foam glued to the bottom so it won't rattle on the cover plate - that pretty much sets your break angle.
When I built my tricone I set the neck angle so the fret plane just hits the bridge without the insert in it - that gave me a reasonable amount of saddle to make the final action adjustment and it cleared the cover plate fine
With all of your thinking about geometry add one more confusion factor. Most resonators have no bridge compensation - the saddle is exactly at the scale length. If you play a lot of fretted stuff it will be sharp, particularly if you have the action a tad high for slide. Consider adding a little compensation when you lay out the cone well - your slide will still play in tune (you have the ultimate compensator on your pinkie) and your fretted notes will be much better. I think I put about 1/16 on the treble side and 2 or 3/16 on the bass side of the tricone - I play about 50/50 fretted and slide.