1. I figured you were a tinkerer. I plan on build a turbine engine from an old turbochager this winter. No reason whatsoever. It will just be cool to fire it off.
2. A 1/6HP unit will not do the job. A 1/6HP unit will do about 800 BTU/HR @ 90 F ambient. Touch more when cooler, but not enough to do the job.
3. TEV's have a nominal capacity based on standard conditions, for a given refrigerant. You then use correction factors to select it from there based on your conditions.
4. Heat load calc is off. The size of the reservoir does not come into the picture, other than what I said before about the reservoir picking up heat from the surface area. Usually you just insulate the crap out of it and not worry about.
5. Heat load => 150 gal/hr * 8.35 lbs/gal * Cp(1.0 BTU/lb * F) * 0.5 F. Do the dimensional analysis and you get 625 BTU/HR. So maybe the 1/6 HP unit will work after all!
6. I dunno about the twin turbo traction sequential defribillator thingy. I just drive a truck.
7. I would rather gouge my eyes out than use AutoCAD. If you ever want to do 3D check out SolidWork, SolidEdge, or PRO/E. I have been using SolidEdge since V3.5 when I designed my SR. project in college. I now am on V15, use it for all of the stuff I build.
8. Ever though about thermoelectics? Not so messy.
Good luck with you project and school. Don't drink too much beer.