I am/was an ER nurse who went back for BSN-DNP, specializing in Family practice. I understand the anxiety around choosing a specialty, especially coming from an acute area of practice (and from what I'm gathering, likely wanting to stay there?) I should also mention I am a spouse of active duty navy x 15 years, and am using the GI bill myself.
I chose FNP because it's the most marketable, I can treat across the lifespan. In my program, there are at least 50-75% of the FNP program are ER/ICU nurses, who chose FNP for the same reasons as I did. If we want to pursue a post-grad certificate in acute care, it'll be short and sweet and I can work virtually anywhere.
If you are undecided which clinical area you want to work in: FNP
If you are 100% certain you never want to treat kids, and you mentioned you want to stay in an acute setting- take ACNP
If you're 100% certain you don't want to treat kids, but aren't sure of your desired area of clinical practice: FNP (as opposed to AGNP)
ACNP really ties you to a hospital or outpatient center. For myself, I was tired of working all hours of the day/night and was looking forward to getting on "normal" hours (or at least daylight hours). I would also consider where you want to live. Larger cities require more site-specific quals whereas the more rural towns flex a bit more (FNP's often work as hospitalists, for example).
I am now 8 months away from finishing with my DNP- I write my AANP exam next month. Considering you're a single guy without dependents, get your DNP. It doesn't matter all that much in terms of clinical practice, but as more and more DNP's enter circulation you're quals will be somewhat lesser then others (if only on paper). If you don't want to get the DNP, then I'd go after PA instead of NP. Shorter, you'd likely stay in acute if you wanted to, less liability as no independent practice, etc. Lastly- go to a brick and mortar school, not online. I did, and I am very glad I chose this way. Some people elect for online for cost or convenience, but if you can afford the brick and mortar (thank you GI Bill, and thank YOU sir for your service) then do it.
PS- 80K a year is way, way low even for a new grad NP. Average is at least 90-100 for starters. I purposefully omitted CRNA info, as I know you said no to that one- those guys make 120-150K.