1) There isn't such thing as safe while running on cfw, although having the latest one is always a good idea.
2) Your drive does not support ap2.5/6, so there's no need to even patch the iso's with abgx, your backups will boot regardless. The LT+ 1.9 cfw for your drive was made after the flashing of M$ took place at the end of last May.
The recent 13599 dashboard made ap2.5 games not boot again on the other drives you mentioned (Ap2.5 supported drives), so there was a need for a new way to handle the new (random) checks. That was nicked Ap2.6, and LT+ 1.91 is "handling it", so that backups can boot fine now on this dashboard.
I hope that gives you a bit of a clue about this Ap2.5 stuff, It surely can get confusing sometimes...
So that means ALL toshiba-samys dont support ap25 or only ms25 drives, like i said im not sure about wheter i have an ms25 or ms28, and Im not going to disassemble my case with a screwdriver (it destroys the case), ill have to wait till i get the tool from team xecuter.