Hi Neil! Welcome. Speaking as a dev whose games would be mute without the generosity of composers like you, I say more music under free licenses is always welcome. So thanks for sharing! To answer your questions,
- Of course your library can be useful! I actually heard some music in your Soundcloud I could have used in an older game. But I closed the tab, and now can't find it again. Never mind -- point is, you never know when someone out there might need what you make.
- Speaking from my experience as a game dev, and from what people say on Open Game Art, it's a lot more useful to have a music album (or any asset pack) that's thematically consistent than a bunch of mismatched pieces. Even mixing and matching gets easier -- and one always has to mix and match when reusing assets.
- My go-to place for reusable game assets is the aforementioned OGA, but the asset section right here on itch.io is quickly catching up. The one time I had to scour Jamendo for a soundtrack, it took me days (ugh). Long story short, you're already here, why not take advantage of it.
- Licensing is a thorny issue. Most important factor is that any license that prohibits commercial reuse makes your music off-limits, even for a freeware game. And people who want to make games for the Apple Store or Steam will have to avoid Creative Commons because of the anti-DRM clause in that family of licenses. (Unless it's CC0, of course.) But I apply them to my work precisely because I'm anti-DRM. At the other end of the spectrum, some creators favor the General Public License, but it's officially not recommended for anything but source code, and it's also one of the hardest to comply with. Yet people still use it. But the most popular these days are liberal open source licenses like MIT or BSD.
- As for your last question, if I could afford to commission a composer, I'd go straight to my friends instead of digging through free archives...
Hope this helps.