The problem with the Neph station is that it is too powerful compared to both Confed's and the Kilrathi's. Reducing the number of those nasty outer rock turrets should even it out.
Also the Barracuda seems rather nasty for just a corvette. It attacking damage is fine, but I think its HP is too high.
I think a little reordering is in order though for the ships: the Orca destroyer I've always seen as being more an anti-destroyer/corvette/frigate ship especially since it has fewer anti-capship weapons. The Hydra though I see as being quite a bit nastier with those three prongs. The Leviathan (fighter complement of ~200) I think should be at least one tier higher while the Orca (now reduced in effectiveness) could be placed into the Tier 1 with small complement of fighters (~20 in the canon...kindof). From the games, the impression is that the Neph fight more in a swarm like fashion with more and presumably cheaper ships. There would also be a better match up I think between the Durango and the Orca (maybe 1.5 of these) actually in role. Especially I think the durango has a complement of 30-40 ships.
The rest of the tech tree seems alright to me for the Neph with the Leviathan at tier 2, since it is rather quick compared to most everything. Btw, this document, while not officially canon and containing some inaccuracies, could prove useful or of interest:
https://www.wcnews.com/chrisreid/shipsalien.doc
As for the fighters, you picked some curious craft to make bombers: the wasp (an interceptor) and the Eskhapi (an atmospheric fighter). Really fighters/bombers are rather minor concerns (ie nitpicky), I still think that more traditional bomber type craft would be more fitting. The vaktoth would fit well for the Kilrathi light carrier bomber role, but for Confed, I'm not sure. I see that there is a crossbow here (never saw him in battle though). Btw, what are the heretic, X36 and Foxbat supposed to be? In any case, if you don't mind adding another craft you could include the Thunderbolt or the Sabre to fill out the light-carrier bomber craft role. If not I would think that switching the T-shark with the Wasp would feel more fitting canon-wise (though it also marginal as the T-shark is just multi-purpose and not very heavy).
In any case, the fighter thing is really minor and not worth a bunch of extra work on my account.
For the Midway, Kraken and Tiamat I was expecting something more along the lines of at least being able to wipe out corvettes and light destroyers (like the Murphy) in one blast. Canonically however, the weapon should take out a fleet of 5 heavy ships in one blast but for the sake of balance, we can just assume they are using lower power settings and short cool down cycle (especially in the case of the Midway as it should blow up when using it more than once).
As for music, well it doesn't matter too much at this point. Something either from the WC games or fan-made by one of the communities talented musicians would be nice. In any case though, I'm just playing wc music in the background with the in-game music off, and wow what a difference it makes. For speech, while you could get a few people to record some quick lines (something that shouldn't be too difficult considering Standoff has done it with 10 to 20x the number of voice-actors and 100x the number of lines that this project would require. Granted, new speech may not be possible, then I definitely think the speech should be turned off.
