Game Mechanic/ General Help Questions

I was wondering about how damage is shared between units. I had 2 tactical bombers attacking 3 infantry, and it said the bombers had 52% HP/morale, but after attacking 1 bomber was shot down, and now the other has 88% HP. If I understand corrrectly the bombers must have had different HP at the start of the attack and the 52% was an average. Is there a way to see the HP for individual units inside a unit group so as to not use low HP units in battles?

Another question is about infrastructure, and how much to develop it. Due to the 75% penalty on resource production in non-core provinces, is it worth it to build infrastructure there? Also in provinces that only produce manpower and cash is infrastructure all that important? Is it worth it for the money/manpower and speed bonus but no resource bonus?

Thanks in advance for your help