First, it sounds like you are in a good position and have a good head on your shoulders. When you evaluating which is the better of several good choices, you have already won, so congratulations.
My biggest concern for you is appropriately protecting your downside risk, which means identifying what might happen and figuring out a plan to mitigate those risks (yes, I am a total ray of sunshine). For example: disability. You aren't eligible for LTD, which sucks. So what that means is that you need significantly more money in accessible savings/investments to be able to tide you over; you also need to be thinking of some alternate job plan if you need to support an earlier-than-expected retirement. As you know already, you have a very physically-demanding job. And as you start to get older, the body starts to get less forgiving as all those little ways you misuse your body start to add up. All it takes is one ruptured disc or something like that -- you'd certainly be able to continue working, but probably not as a firefighter. So what's the backup plan? Would you go back to school for some sort of retraining; would your wife go back to work, and if so would she need more school/retraining; and if so, how would you cover that? Etc. No need to make dramatic changes, of course, but those sorts of concerns suggest that you may want a bigger EF and/or to put your extra cash somewhere you can get it without penalty (e.g., maybe the Roth is better after all, because you can withdraw the contributions).
Also make sure you are considering longer-term irregular costs in your budget and putting some aside each month for that. Your cars will need new tires and periodic $$$ service, and you will eventually need a new(er) car; the house will need a new dishwasher and roof and HVAC and 800 other things; etc. If you budget for that kind of stuff every month, you don't need to worry when those expenses pop up.
Finally, it's a good idea not to make any big plans about career or OT or anything like that right now, because at this point, you don't yet know what life is going to be like when your oldest starts school. Maybe there will be extra expenses that you're not even thinking of now -- field trips, school supplies/fees, peer-pressure purchases, after-school activities and lessons, etc. -- and you'll decide that you want to continue working a lot of OT to cover those extra costs. Or maybe you find you really, really miss all the extra time with your girl now that she's in school all day, and you decide you want to stop with the weekend OT so you get the time you want with her. Or maybe in 10 years you're just done with the firefighting; as much as you love it now, you don't know who you'll be in 10-15 years. Again, the best thing you can do is sock away as much as you can right now, while you have so much OT available and you're really enjoying your job so much, so that if your goals or priorities change in a few years, you have the financial freedom to make whatever decision you want.
(Oh, and finally-finally: stop spending your HSA on current medical bills. That is by far your best supplemental retirement account)
