Try 70grs 2f fire a few then work up in 5gr increments up to 90 or so,obviously cleaning bore between shots. Whichever groups the best will be your hunting load. You have to see which load your particular gun likes. Believe its a 1-48 twist so generally a shorter/lighter bullet stabizes better. My 1-48s shot 245gr aerotips the best as far as powerbelts go.
I use 90gr of 2F in my Deer Stalker, 240gr Hornady xtp and 265gr Hornady Interlocs. I started at 70gr when I first got the gun, group got better the hotter the load got.. didn't see much difference between 90gr and 100gr so I stayed at 90...
My first flintlock deer was shot with a Deerstalker, 70 grains of Pyrodex P and a 295 Powerbelt at about 60 yards. Complete pass through the rib cage. I never shot them any hotter in the flinter. I shoot mostly round balls now with 70 grains of 2F Swiss. I broke a does shoulder with that load.
The Deer stalker is a bit short to burn a lot of powder. I got that advice from Dixon's in Kempton.
Go ahead and experiment. That's the fun of having a muzzleloader. The load options are unlimited.