1) In this DLC I gladly use RPs for aux conscripts and regulars because they cost so little and you get a 50% refund. Was it sthg like 5 RPs (= 2.5 net) for 5 str pts for conscripts. It's a bargain! Don't upgrade units unless it makes sense is one of the best advice in OoB. Also consider upgrade paths. Some units don't have any.
2) Strategic bombers are especially useful in this DLC because the early Soviet tac bombers are rather bad.
4) Play smart - definitely. Do only what is required to fulfil the objectives and don't rush needlessly. Just like Bru is playing better, I have changed my style also. I use all the turns available and advance cautiously thereby minimizing damage to my core units. In defensive missions I try to do only that.
OoB surely deserves someone who takes care of the single mission players - whether there are any others than him or not.

Nice trophy, Spike!