Just watched the complete replay and I must say that I don't believe anyone was using maphacks.
If you compare this game and some of the stuff guys like rtn.raz and KinderPartySmackdown have been doing back in the day, this is nowhere close.
The Schwerer was accidentally discovered when he legitimately shelled the path of assaulting units after mass retreat. After that, he kept shelling Schwerer because he knew where it was.
All other instances of "lucky" pio hits while repairing stem from the fact that you always took the same path when returning to the field after mass retreat. He took advantage of that and shelled it while getting lucky because you kept repairing your P4 in a pretty bad spot.
Another reason why this game is clear is the fact that he didn't chase down your P4 when it had just a sliver of health and was getting repaired unsupported. Had he been using hacks, he could have easily rushed in with T34 and t70 and knocked it out.
Well played by him.
I think the best way to help new players is to provide them with a top to bottom build order and ask them to execute it to a T.
For example, start with 3 tommies, mg, tech up, get pios, at gun, tech scout car, get scout car, get some doctrinal unit, tech up, get cromwel, get firefly.
This may not be the current meta nor could this build work, but you get the idea.
Once they start feeling comfortable with the timing of the build order, things will start to flow naturally and they will get the idea how to adapt on the fly and try to modify unit selection to react to the actual threats or push the advantage.
Another important aspect is manpower control. Too many model losses set you back tech wise and disrupt your plan. It is better to hard retreat early then stay in an engagement and bleed. Unless you are under critical VP bleed, there is no reason to sacrifice your MP to capture a particular point. Retreat, regroup and send reinforcements that are capable of resolving a particular situation.
Map awareness and understanding importance of strategic points is also important to grasp. I am talking about strategic buildings, cutoffs, and general areas where enemy presence is a pain in the rear end. Making a decision when to leave those areas undefended to chase some harassing units is one of the biggest mistakes new players make. Similarly, taking advantage of such areas when the enemy makes a mistake is also something a new player should pay attention to.
Finally, it's all about practice and learning from the losses. If he is stubborn and wants only to turtle, he is not gonna get far. Sure, he might face some new opponents and beat them, but once he steps up on the leader he will get mowed down hard unless he objectively analyzes what works and what doesn't and why.
I would also not insist on micro perfection and the APM as this aspect of the game will gradually improve with practice. In coh2, it is far better to make correct decisions then to make quick ones.