Very sorry for your loss so early on.
I keep hoping
@dave_person will chime in here, or another of our well researched builders, as I'd hate to see you not get as much h as possible if you do sell it, and he (as well as others like him) really have this stuff nailed. I'm also wondering about a couple things that to my novice eye seem, different. The 2 tiny wood screws on either end of the side plate for instance. I'm assuming the use of the nut to hold the cock in place was done at the time of conversion from flint to percussion, but, I don't know for sure. Someone like Mr. Person might also know what can be, and should be, fixed, and how it will effect the value.
Can we see a pic looking down at the top of the barrel to include the tang forward to the front end of the lock please? Also of the muzzle with something for size reference? Have you measured the bore, even just a simple measurement across the diameter?
On a more personal note regarding selling it. I and in a mountain of debt, just spent a few months out of work, and the last few weeks with no pay from any source. I need tires on my truck before the snow flies. I kept a nice cedar closet and a cedar blanket chest, among a few other smaller things, from my grandmother's house after she passed away in January. If I sell any or all of these things and buy tires (or groceries) with the money, in a year and a half to 2 years, I will need tires again, but I won't be able to replace what I sold. I've done this dance before.
If we go with the early estimate that it is only worth a few hundred dollars, is that really enough to fix your financial situation? Or just a band-aid on an axe wound?
To be honest, even though I'm on the "don't sell it" side of things, I wish I could buy it. It seems a little later than my general period of interest, but, something intrigues me about it. If only it could speak.
Not sure if that is a "D.5." or "D.S." crudely carved into the stock. If "D.S." I would assume it to be someone's initials.
I wish you all the best.