Well, you can get powder sent to you. Grafs is a good source for lesser quantities of real black.
If you must use a sub, try Pyrodex. It has better ignition characteristics than t7 although still not as good as real bp.
Drilling your nipple out may improve ignition but it will make your rifle less accurate. Also, 90 grains of any powder is not likely to deliver good accuracy in your deer hunter. FWIW, the last deer that i killed with a deer hunter was a full grown mulie doe at 80 yards with 60 grains of 3f powder. Don't over estimate how much powder you need.
As previously stated, .10 patches are pretty thin. Check out your fired patches and see how they look.
Fired patches should look like this.
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