Your math seems good to me. The one extra factor to consider is that larger contracts tend to go cheaper per point.
This past summer I paid $121 for 160 points at BLT, then $185 for 25 more ($24,000 total). Had I bought 200 at $115, it would have cost me $23000.
Yes, I could have had 15 extra points for $1000 less, assuming I could have found a contract like that, but I would have to pay more in MFs for them, and I would be missing out on the perks that I am already enjoying.
I have loved the resale + direct add on combo. If I find that I am ever running low on points, I can use my discounted AP to get a discount on resort hotel rooms, or can use my AP to get free parking as a stay at a resort off property. It opens up a lot more options for me.
The problem is that they have started to indiscriminately alter the perks.
For instance: with rising costs driving down attendance in Florida parks...they gave a great AP discount for 2018. The logic is that won't happen with Star Wars next year...
I was sure of that 4 weeks ago...then I saw the recent movie and I'm only 80% sure.
I think that future demand could all but eliminated dvc perks...it's a captive audience and parks are about to Become their primary profit center. If they don't have to lure you there...they will not.