Just one thing really made no sense

Totally agree

That part was fiction. The movie had to end with a one on one with glass and fitz. If they took an army that couldnt have happened.

Lol I said the same thing when I saw only him and Glass riding out on the horses. Like, wtf.. where's your army? Just you and a guy still healing from getting his ass kicked by a bear?

Either "WE" f*<kin or "I'M" f*<kin- Bill Cosby

I thought the same thing.

And, no, I'm not referring to anything regarding Glass' almost superhuman survival. I took all of that on faith, as the human instinct for self-preservation can transcend some truly extraordinary obstacles.
No, the problem I had was with the fact that Henry took only himself and a gravely wounded Glass to track down Fitzgerald. Knowing at that point that Fitzgerald was a killer, it was sheer lunacy for Henry to not take at least two or three (or more) additional men. Of course, the point of it was to easily set up the mano-a-mano confrontation between Glass and Fitzgerald, but need it have been so obvious a contrivance?

Yes, especially since the film had established that he could put together a sizable search party. Total contrivance. Kind of ruined the film for me.

I think this can be justified. When Capt. Henry and Glass head out to locate Fitzgerald Henry cries that the wage for this will be "ten dollars a man". Now, if you are in the relative comfort and security of the compound, it's New Year's Eve, you're in the mood for some R&R, would you want to venture out into the uncharted, icy wilderness to find a man who has done nothing to you, is more than likely long gone, risk being attacked and killed by various native tribes, and, even if you do find him, you might end up on the end of a rope if he gets killed as he had signed up to the army? And all for ten dollars? I can see why Capt. Henry and Glass would have a personal reason for chasing Fitzgerald, but would others, unconnected to the previous events?
Getting a search party together to rescue a highly regarded scout is one thing as it appeals to the Samaritan in us all. But getting a party together to hunt a man down, to risk lives to find him, only to bring him back to be, in all likelihood, executed is an entirely different kettle of cod I'd say. Let the wilderness, or the natives, or a bear, or starvation, or any number of likelihoods do the job for you without risk to anyone else.
So while the story's arc required a man to man face off at the end I think the method by which it is achieved is valid and justifiable.