If you're used to using Black powder and want to switch to a cleaner 'substitute' powder like Pyrodex, be aware, by actual weight, it is not the same. 100 grains measured by volume of Goex FFg is about 101.3 grains by weight. 100 grains measured by volume of Pyrodex RS is about 72.5 grains by weight. So you would have to play around on the range to figure it out. By the By...90 grs of Goex may actually be on the heavy side.
Most guys use pellets for the convenience, but I find loose powder will give you better accuracy with 80-90 grs of Triple 7.
I used to do the dogging for the camp (ohh to be young again) and I hated having a scope on it...never trusted that it didn't take a whack and that it would be holding zero. So I stuck with open sights, but as I got older and the eye sight began to wane and I could not longer focus on the rear iron sight, so I was forced to put on a scope.
Small shotgun scopes work well, as Big Jack mentioned, they are built to take a kicking. I also found Red Dots, which I prefer for fast target acquisition, are great for bush hunting, but have to be monitored to ensure they are holding their zero.
As far a bullets....I like a heavy (300+ gr), soft lead bullet for short range shooting. Prefer to have max energy expended in the body cavity and not too concerned about an exit wound. Most deer I've hit drop where they were standing or within sight. Never been an issue in 20 yrs.
A new gun...ML's aren't a huge investment, a lot of them they go on sale regulatory for around $300 and will hit MOA at 100 yrds out of the box. Great for short range hunting. Maybe a change would help with your confidence, which is very important when you see that 'Rack' in front of you.