By under-lever, do you mean what we call
lever action (as in cowboy rifles in the movies)?
I worry about your black powder pistol laying around for months with corrosion and chemical reactions ... Do you really have to use black powder? Or, can you use modern black powder substitutes?
This article explains some of the nuances:
http://www.chuckhawks.com/difference_black_powders.htm
If I could have a rifled barrel lever action "shot-gun", I'd take that over any pistol any day. The impact is much greater and can develop shock enough to really slow things down. The boom will put the "other" on the defensive and maybe their compatriots ... Hearing the action working and knowing another is coming is not a pleasant thought... It's not the sound of pump wracking, but it ain't that far off.
A rifled barrel shot-gun with a Red Dot sight, with both eyes open so you have maximum situational awareness, is good thing. Getting hit with a shot-gun slug is not ... It is a very big impact.
If you want to test this, get some 4~5 liter jugs full of water and hit one with your 44. Then hit one with your shot-gun slug. You will see that there is a big difference.
What do the other people at your gun club have?
I'm in sympathy with you'all. You have been hit more than we have in the last year. I fully understand your desire to be able to take action if need be. Be safe.