Leah,
Thanks so much for your patience in hearing back from me!

I am knee-deep in planning my older son's sophomore year, as I haven't had much time to do that until I finished the new guide first!
In the math plan you shared, you will indeed be done with Pre-Algebra quite quickly. It is a short introduction course. I can't remember exactly but was thinking it took us about 6 or 7 weeks. If a student isn't a very quick worker it may 9-10 weeks at the most. We just set our timer for 45 minutes a day and did as many of the lessons that fit well within that time frame.
Then, once we finished Pre-Algebra, we headed right into Videotext. This worked well, as Module A of Videotext is also Pre-Algebra (but done in a different way). Don't be surprised if the beginning of Module A seems heavy. Just keep on going and it gets easier. There is MUCH content in Module A.
The shorter burst of Pre-Algebra Math Essentials will help jump start your son's year without pulling him too far back so that he is behind schedule in the math he needs for science.
As far as Teaching Textbooks goes, you could easily do as you scheduled above with TT Geometry and Pre-Calc. If you did choose to use Videotext instead of TT, then it is true that the geometry and pre-calc. and trig. are somewhat interwoven in the modules. So, you'll need to decide whether to go the TT or VT route for junior and senior year. You could easily wait to decide until you get there, after seeing how well you like VT for Algebra.
We did see the new Algebra by Math Essentials. We actually took a detour from VT and did much of the pilot version of Math Essential's Algebra online last year. We really liked Rick Fisher's step by step presentations, but there wasn't nearly enough practice or any review. Being in the pilot stages, there were also some errors in the answer keys in Math Essentials and no fully worked solutions. These things may have been corrected in the final version they're offering now. Over time, I really missed a full-text answer key with step-by-step solutions for every problem like we had in VT, the course notes from VT, and the daily quiz format with VT. The online Algebra didn't feel nearly as full or thorough as VT. Needless to say, we ended up back at VT the last quarter of last school year and really flew along with it, just picking back up where we left off. I was glad to be back to it and so was my son. We won't detour again in Algebra. If your son likes Rick Fisher's presentations, then a look at the finished product may be worth your while, to see if review and more practice have been added.
Blessings,
Carrie