I use 150gr of 777 and powerbelt bullets all the time. Especially when November rolls around and the temp drops. When the temps drop to 20 and 30 below it takes that amount to get the bullets out to 100 yards. Don't try and shoot anything beyond 125 yards, the bullet won't get there. When the kill zone is two feet in diamator, accuracy is not a problem, velocity and energy is. As you may have noticed I'm not hunting whitetails, I am hunting Moose. I also use it for Bears, same loads, same concerns, energy and velocity. At bears I am only shooting 15 to 20 yards, so again accuracy is not a problem.
But in your case I would use 110 to 120 grains (volume equivalent) of 777. My best accuracy was sith 80grs, but range and velocity suffer. The reason I use the power belts is that they are the only bullet that will load when the temps drop. Anything with lube on it freezes solid and will not load. Same with sabots. But the power belts will load at cold temps, and you can reload them two or three times without cleaning the gun between reloads. That's important when there is a possiability that your quarre can kill and eat you. I hate going into the alders after a wounded Grizzly.
I use the T/C Bore Butter, the T/C cleaner, and the T/C lube on the Breech plug. I use a tiny nylon brush on my dremel tool to keep the threads clean for the breech plug and in the reciever. I have always used Federal 209 primers, when I started shooting Inlines Federals were the hottest primers. Now I think there is other primers that may be hotter, but that's what I am used to and I can't see breaking up a winning combination in my case. The nice thing about the 777 powder is that it does not foul as bad as Pyrodex or reguler Black powder. A solid brass rod is invaluable, because sooner or later you are going to pull the trigger and it will only go pop. You forgot the powder, and the primer drove the bullet far enough that it is really stuck. Your ramrod is not strong enough to drive the stuck bullet out. I use a soft brass rod to drive the stuck bullets out, that way I don't damage anything. This rod goes to hunting camp every year. I glued two small sleeves onto my Koplin case, one carries that rod and the other carries a spare ramrod.