Hey. I don't know the answer to 1. As you know, no doubt, the F4 option indicates on the counters some idea of combat strength, though not one I've ever really paid much attention to, to be honest, because there is so much detailed information about numbers, morale, experience etc etc in the 'Force' window and I've always gone off that when planning. In particular, fatigue levels, of course. If you select an HQ then it will give info about the HQ in the Force window in the left column, then about all subordinates (aggregated) in the right column. But I don't know a way to get a kind of aggregate combat 'number' for a Bn etc. Someone else might have a clue.
As to moving and positioning the HQ alone you will have to detach it, in effect, which - as far as I know - you can only do by giving separate orders to the HQ and the subordinates. That is, select the subordinates (you can lassoo them, or Cntrl-left click them in turn) and give them some order. Then do the same for the HQ. Once the HQ is in the position you want it then you can click 'reattach' for all the subordinates. If you want them all to remain in the new positions relative to each other (as you would when Defending, perhaps) then once they're reattached give the HQ a new Defend order with 'in situ' selected. Carefully positioning an HQ in respect to its subordinates for an Attack is more complicated because once you give the Attack order to the HQ and attached subordinates the HQ will plan its own attack route etc and I know no way you can control that in detail except by giving separate orders to every unit, which is not really to do a Bn attack at all, of course. You can get some measure of control as to where the HQ will base during a Bn attack (say) by manually placing the forming up point for the attack. This you do by selecting the HQ (with all participating units attached), selecting Attack, then shift clicking where you want the FUP to be (same way you place waypoints), then after that placing where you want the Attack to be. The FUP is always the last 'waypoint' before the Attack marker. The HQ will base in relation to the FUP marker.
Sorry if this is all stuff you knew already.