Hi neighbor! We're in PNS too

If you and DH have the CSP and CSR (DH and I are the same way) then maybe the United card would be beneficial if you find you use the MPX (which I love) a lot for the 25%. That said, United does fly most places (with a connection) and I tend to keep a stash of those.
Most people find a lot of value (1.5 CSR and 1.25 CSP) by using the travel portal from Chase so that would include AA and DL flights IF you don't want to dabble in other flexible currencies. I'd look at my Chase profile, max it out (a business card maybe?)
then get an AA card (if you haven't had a bonus from Citi in 2 years OR Barclay...I believe Barclay has a card with
1 purchase and current offer is 50,000 miles and paying the AF of $95). Citi also has an AA card but its website is
horrible and I despise using it.
Delta miles can be used from SPG (soon Marriott), Amex MRs (flexible with other partners but I don't believe SW) and of course co-branded Amex Delta cards.
Before the Big Merge I focused on MRs and SPG for flexible points (since I primarily fly Delta and occasionally American). Now I look at Delta and MRs since again I focus mostly on Delta but do have around 250,000 united miles and until this week 350,000 American Airlines miles. I try to keep "currencies" in the 3 big ones plus MRs and URs. Since you frequently fly SW URs are still probably your best bet, then deciding which of the big 3 OR MRs to be a secondary stash.
To summarize:
Overall best is to max out UR (would a CIP/United or other card help you more with this?).
Decide whether you want to collect individual currencies (united, aa, delta) or continue to focus on general flexible stashes (Amex MRs or wait and see how the Starriott merge shakes out).
Hope this helped somehow