Follow the playlist provided by the OP and that will save a lot of frustration. You will know where and how many enemy will appear in the next corner. However, it's still very hard on Veteran.
For the Dam mission, right path is easier on Veteran, because if you choose left, two enemies will spawn behind and above you after you pass a certain point, which is really harder for you to take them out and always results an instant death (freaking accurate riflemen). You will get a checkpoint right after you step out the elevator. Be careful though, three or four guys will rush to your point. Better take them out before you step out. From there on, it gets a little easier, but still hard. Prepare for a lot of close-quarter combat (still using your submachine guns).
The next checkpoint you will get is where you step out of the room after the long corridor.
The one after is when you destroy the last flak gun at the bottom of the dam.
In mission Pavlov, when you are about to destroy the tanks using anit-tank guns, just destroy the two indicated by the mission objectives, then hide at one of the corners around you at the 3rd floor near the broken windows. Go prone and kill anyone coming near you. When the counter is 2:00 left, you get a checkpoint. Jump out from the broken building and go WEST (not sure, the direction without the third tank). Go prone behind a small wall, and prepare for any incoming enemy, and let the time pass until all the enemies are killed by your allies.
This probably doesn't work 100%, but at least you can try if you're out of ways to pass the mission.