For the first question, you would use some other button on the keyboard to click while dragging. I use the trackpoint which is also not pressable, but I use the mouse layer key to click. My mouse layer is activated with the mouse key in place of caps lock and a left click is with F. Since the UHK is completely mappable, you can find the best key combo for yourself. Only your thumb is occupied on the trackball so you have 4 fingers left for clicking on that hand alone. :)
If you get the left side key cluster module, it has clickers on the edge, so you can use those for clicking with your left hand while dragging with your right. Personally for me it wasn't the most comfortable choice so I stick to my mouse keys.
This is actually my first trackpoint that I really use, so I haven't searched for any alternative tips. I do admit a PS controller stick could be nice. :D Maybe a bit too light to touch?