Math sounds spot on to me. I generally hit the numbers that you list, and my historical return on spend (ratio of best available rate for nights redeemed / total spend at Hilton) has always been in the range of 20-25%. The 49K marginal points is probably around about $250 in value (so that takes the marginal cost down to 450 - 95 - 250 = $105). If you use the resort credit, airline fee credit, and/or WA/Conrad credit from the Aspire you come out ahead. Annual weekend night is a wash because with the Ascend you'll still hit the spend requirement.

I've been a 50/50 Hilton/MR guy lately, Diamond at HH and Plat at MR; I've found my personal return to be better at Hilton, YMMV. I think that for someone doing as many stays as you, splitting and getting top tier at both is a good diversification play (especially if you're going to places where the footprints might be complementary or one chain might not have a presence). Just my opinion.