you're on the right path. I am 6'2" on an XL rise. Typically, my preferred reach is about 485-490. The XL feels long/big when in full 29 due to the reach and the length of the seat tube. I too noted a feeling of the front end tucking on high speed berms and awkward sections. I have since converted it to a mullet as well and extended the fork to 160 (i also put 160mm cranks on it).
The combination of the bottom bracket drop offset f/r, head tube angle and increase in stack height have eliminated the front end tuck feeling for me as well. I didn't mind it before as it's a sensation that I experience often on xc/trail bikes, but it became a bit un-nerving at speed.
I would also re-visit your rear sag and ensure that it's correct. 240psi seems like quite a bit for 90kg. I would guess that your rear sag is around 25% or so and really, I think 30% would be a bit more appropriate.