Okay, got it. Hollowed-out middle, not a great company, not much above you. Yeah, that changes things.
So here's a question - do you like bookkeeping? Because actuarial exams and CPAs and the like are definitely continuing ed stuff that helps the company out if you take it on. And they make you more valuable for the next place. And hey - if you step up and fill in while the bookkeeper is on maternity leave, that makes you a department head! W00t w00t! and if she comes back (maternity leave is a life-changer) you have an excuse to move on somewhere else.
The raise issue isn't a good one to pursue - you aren't going to get more scratch without more responsibility and by taking on more responsibility you look more attractive to other employers. I'd get with the bookkeeper and say "I want to do your job while you're gone and if you come back, I want enough skills to do something else. What do you recommend?"