I'm not trying to pretend to answer your question. I can't hope to say what is best, especially for someone who isn't me. But I will at least attempt to order what I've tried from what seems to have worked the best for me to what has clearly worked the worst. I do feel the need to point out you're working on something more ambitious than anything I've attempted. My history isn't that good; I've never had the guts to try writing something in a defined historical real-world setting. Most of the suggestions I'm going to give at the end of this were things people gave me as advice, and I've found at least some utility of them.

Feel free to skip down to the next horizontal break; the stuff between here and there is appendix stuff I just don't want to risk looking like my conclusion.

I have used the following:

• I've set up a wiki on my home computer, localhost only, for several of my stories. Each character gets a page, and each time I write new things about the character, I try to update their wiki page. Their page starts off with what story or stories they're in, because I have accidentally put a character in the wrong story after I started with the wiki concept. But once I got that fixed, it hasn't been too bad. What exactly goes in to each wiki page varies widely by the character, but it at least starts off with how they're associated with the most prominent character not them that they're associated with, and then lists their various relationships and details some notes with them. Characters with quirks tend to get much more written about them than others. If they have an accent, that might include everything they ever say as a reference.

• I've kept text files with notes about all of the characters, one file per story. The same sort of information goes in there, except it usually doesn't list multiple relationships for characters, and it won't include quotes or as much background, just because of trying to keep all the data roughly proximal. If there are characters with accents, there will be a second file for quotes.

• I've kept text files, one per character, sort of like a wiki. The best result of this effort was it gave a proper seed for the start of the wiki. The worst bit is navigating through dozens of files without using hyperlinks is rough. The worst part isn't finding which file to open, but rather which window to switch to. Microsoft Word's inability to have more than one file open per file base name could come in handy here.

• I've used an actual database. If you're going to go down this path, I'd strongly recommend that you use an off-the-shelf solution written specifically for the purpose. Trying to write my own thing is not beyond my computer sophistication. But trying to write my own author details database while also trying to write a story is an excellent way to forget what you were writing about, because the glitches in the software will come out at the worst times. I think maintaining explicit fields for the various sorts of data is probably overkill; if you have a wiki and you have discipline, that works.

• Re-read the story whenever I'm at a loss for who a character is. This tends to break down around chapter 2. Wait, who the heck is this Mike character? That wasn't who Giselda was talking to! How the heck did I go from her talking to Sfen to Mike? Um, wait, it just literally stops with Sfen in paragraph 12 and starts with Mike in paragraph 13? Oh, crap, Mike was the guy from that other thing. Edit edit edit.

• This was a really intense dream, I don't need to keep track of my characters, I know all this stuff.

In going through all of that, I knew when I needed something better as far as tools when I got to the point where I couldn't keep track of what I was doing. But there always was a time before that I felt uneasy about how I was proceeding.

As far as keeping track of characters and how to best figure out the tool, I'd think I've actually had the best luck practicing that with somebody else's work, especially web comics. If I lose track of a web comic's characters, it's no big loss. But I can at least determine whether the mechanism is sufficient for handling a cast of that size. That said, if you have your 107 characters now, I'd strongly suggest at least writing an outline of all of the characters you don't already have at least an outline of before you think about focusing on something else. It's preferable that you jot down as much as you can in that outline, especially bibliography notes.