There are several threads similar to this under Forums > Destinations > America > USA > Hawaii, including this one:
72-Hour Pre-Departure Covid Testing (Experiences Only)
Although CareNow is not listed separately under Hawaii's list of tested partners, they are a subgroup under American Airlines. My negative test from a CareNow facility <72 hours prior to departure allowed me to avoid the 14-day quarantine 3 weeks ago. Of course, HI's requirements are constantly being modified, but what AA told me would work did.
Regarding your question about testing within a 2-hour layover, that would be tight, especially if changing terminals at DFW, but it's not impossible. Again, the threads on this under "Hawaii" will provide more insight.
Also, be aware that not all CareNow facilities in the DFW area are offering the test required by HI. The information on AA's website should list only those facilities that are participating in the program. Good luck.