Best to start with 50 grains of 2F for plinking and target. If you are hunting then between 70 and 90 grains 2F will work nicely out to around 150 yards. You will have to tinker a bit to see what load gives you the best accuracy at the distance you are shooting, bit those loads should get you in the ball park.
Best thing for you to do is find a gunsmith.
Best to ask a gunsmith for assistance.
Your best bet is to contact Marksman directly See the link below
you probably just stop and load.
A magazine
Put the ammuniton into the magazine and put the magazine into the rifle, cock it and pull the trigger..
No they won't fit. If you force it, it will ruin the rifle.
Ask a gunsmith.
Possible, but, expensive.
It is a Mountain Stalker. You should contact customer service, and get an owner's manual for your rifle. A .54 caliber rifle will use ABOUT 80-90 grains of black powder per shot. The exact load will depend of whether you are shooting round patched ball, Maxi-ball, or sabots.
ask a gunsmith for help
Yes