Sorry to hear about the band drama, but sounds like you are making progress, and I think your recording is going to rock!
Here is some advice for the recording session itself:
1. You MUST get a producer you trust who is not a member of the band. Musicians simply cannot make objective "big picture" decisions when we are feeling fried and burned out in the studio. Part of a producer's job is to be outside the band and make objective decisions that are not guided by individual ego.
2. Allocate enough time for the bass---don't let them spend 3 days on drums, 2 days on the perfect guitar tone, and then boss you into doing all your bass tracks in 20 minutes, 1 take!
3. Kick the rest of the band out (send them out for pizza or something) when it's your time to do your tracks so you can relax; it should just be you, the engineer, and the producer (whose opinion you trust as I mentioned above).
4. Budget plenty of time to go back and listen to the almost-completed recording as a band and fix/overdub any glaring mistakes or imperfections.
5. Be satisfied, no, be HAPPY with an exciting, entertaining, musical EP that is 90% perfect, as opposed to a technically flawless but lifeless performance.
Out of curiosity, how is this recording project being financed? Is it coming out of band funds? Are you all chipping in equally? Is the singer/songwriter/bandleader covering the expenses? You might find that some of the technical concerns about your playing are actually
budgetary concerns; they are worried about studio costs spiraling out of control. If you are paying an equal share for the recording then demand up-to-and-including-equal time and consideration for your bass tracks, don't let them rush & pressure you into recording inferior tracks, and then tell later you your tracks are flawed.