Audio is my weakest subject area. Fortunately, the person who setup up our Presonus AR12 USB mixer is a still around to help
I take it this isn't for House of Worship? if it is, why 60 fps?
Do not assume audio connections are plug and play. You have to matching outgoing and incoming impedance, gain, etc, and making sure equipment all is properly grounded, etc to get clean audio
I initially assumed you have mic going into the mixer, then a single connection... but 4 Mic inputs in OBS??
Why aren't you taking USB out of Behringer straight into PC? Why are you using the U-22? and are you using its analog or USB output connection? And regardless, you only have a single analog input on the U-22, so regardless of # of mics on Behringer, you still only have a single Audio source on the PC.
There are LOTS of ways to connect a mixer to a PC, and troubleshooting depends on the specifics.
For example, we have all 8 XLR ports connected on Presonus sound board, with Main Out being in-house speakers. We then used the mixers Aux Monitor 1&2 analog output into an adapter to adjust gain (similar to the U-22's analog option), into a TRRS cable into PC, then with correct Operating System settings for that audio input. That provides a single mic input (regardless of channels in use in mixer) for the PC/OBS
To avoid complications, I Disabled all default Audio in OBS. In my scenes, I have the analog audio input captured as a single source, duplicated/referenced in various scenes as required [not all scenes need in-house mic]
We've just installed Presonus' Studio One 5 DAW, and are in the process of configuring it so on the streaming PC I can see each channel individually (via a USB, not analog, connection). However, turns out not so simple as software designed for recording and/or processing and signal going back out to mixer before speakers. Creating a combined virtual consolidated/mixed audio channel output that other Apps on PC can use didn't exist with prior version(4) and even with latest is not intuitive/easy [I'm hoping to avoid a hardware loopback interface kludge setup]. Different DAWs behave differently. I'm using Presonus' Studio One as its free... but unless I get it working without excess complication we may have to switch