Yeah, the production is really nice man. That sounds a bit like some Proteus string stabs in the Fight sequence tracks.
I make beats myself so I'd be interested to know what you use.
Edit. And yes, a pack would be a great idea, but think carefully about your licence, as you are un-likely to make any money off royalties from FPSC users. £20 is totally fair, infact considering each track must take a couple of hours from conception to export, you're really underselling yourself!
I can do beats myself, so I don't know if I would buy, but it's certainly worth it to those users without production capabilites...
..and just coz I'm in a nice mood. If you send me either the fight track or the horror track, I can cut it over some game footage for you (as people might be more encouraged to buy if they can see your work over an actual game. For examples of my editing work go to - www.peanutbutterfingers.co.uk/cutandpieces
Finally, a few other tips for increasing revenue/ usability of the media you're selling.
1) Get in touch with Xplosys at FPSfree.com, I'm sure he will gladly advertise your product. He advertised my, and it rejuvinated my revenue.
2) Perhaps take some shorter 2 bar breaks and individual samples from your tracks and include them too. That way people can activate snippets of the beat, or samples when the player enters a certain zone. I don't know if this'll make sense if you don't actually use FPSC, so here's an example.
*You walk down a creepy corridoor
*as you pass through a shadow, there's a violin stab sample plays
*later, a cabinet falls over and the stab plays again
*you reach a door and a ton of zombies appear, at witch point the violin music kicks in proppery.
I just think people will be more interested if they can implement the whole track, or just elements.
Best of luck. Didn't really intend to write this much... but wahtever, I hope it helps.