I would not worry too much yet. So far DCS F1 radar is just a place holder for the time being... so indeed it does not resemble any proper radar behaviour of F1 radar
I think that Omnibearing is used only in Radio navigation. Using trim hat (0.8deg in pitch, 2deg in az; new heading if longer hold) is to make fine corrections under AP however if used in active Radio navigation it should disengage from it to normal AP.
In DCS for Autopilot to engage, you need to press and hold the autopilot pallet in control stick as you press the autopilot button.
Not idea if that reflects the real procedure
In latest Open Beta, using VR, VTB displayed image is hard to see as it visible only at very limited angle.
What is worse is that since each eye has different picture it can introduce nausea...