Yeah, that's weird. That definitely seems like a very light load. Perhaps something to do with having to seat them deeper in shorter brass, taking away from powder space and upping pressure. As I say, it's the only bullet that light I know of that's intended for .44 mag rifle use, but FTXs also have a reputation for being soft. I've only loaded them in .30-30 and .308, and can confirm that's true for the .308 160 grain at least.
Looking at the Barnes site and they say the XPB will perform well at .44 mag rifle velocities. You mention you can get the Tac X, but the X Tac bullets are rifle calibre. Is it the 200 gr XPB by chance? Though the obvious issue I see there is again powder capacity since they're much longer than a cup and core 200 grain bullet... so the question is can you drive them fast enough? Don't shoot them so I don't have data on them, but you definitely can't use 200 gr cup and core data, so no idea how fast you can push them with H110.
H110 is really a powder that likes heavy charges under heavy for calibre bullets. Doing something else with it is going to be a real challenge. Also which gun do you have? The Marlins have issues all their own with respect to bullet sizes and what they like.
I have a pile of PCd and .430 sized Ranch Dog 275s that come out at 270 gr. I'd be happy to send you some to experiment with if you can use a solid lead bullet. They were specifically developed for the Marlin 94 for hunting. As said, you're already making a .44 hole, and the flat meplat makes them a bit of a hammer. Penetration is also out of this world, they'd pretty much go right through a fallow deer from any angle. No problem to make 1700 fpe with them over H110, but it'll be a max load. PC will give you a bit more velocity for a given charge weight over a copper jacketed bullet, so 21.5gr should get you to 1700 fpe.
Also maybe asked to get this moved to the reloading forum? I'm sure there's more experienced .44 mag loaders there that will have advice.