1) book Hilton points now. Rooms are cancelable. Just call and book an AXON award if you want (which has to be 4 days).
2) Get the Club Carlson credit card (if you haven't) and get a free night on every stay.
3) Do you not have UR points to transfer to United? If so, book stopovers AND open jaw tickets if you want to see more with less. Stopovers do not cost extra.
4) Consider transferring SPG points to AA or UA... but you can wait until you want to book your ticket. I would transfer to United and book trips with stopovers. Message me if you don't understand the stopover thing.
5) Research where you want to transfer Amex MR points to. BA does have those 50% bonuses on transfers every once in a while. Otherwise, singapore airlines for first class suites (if you care), or ANA for more stopovers, etc...

I mean call me crazy but... you could have enough British Airways Avios to go BOS - DUB - AMM - DEL - KUL - PER - SYD - HNL - SEA - BOS. With one program you have enough to circle the globe.
6) Before you do your Marriott stays do a challenge for Platinum status so you get lounge access. Then do status matches to the other hotels if you don't have status already.

I mean really... you should have enough miles to go anywhere so think it out and don't blow them. Feel free to contact me if you need anything.