Here's a trick for getting just a little more Prestige that you can do next time. On Norway, don't take Trondheim and leave the Victory Hex unoccupied (you can leave a unit next to it so no new enemy units appear). Take Nasmos in the north and then wait it out to the final turn (you can now move the unit away from Trondheim if you want some enemy units to shoot at and get some experience while you wait). Now, the reason you want to get a Marginal Victory is there is no penalty (you still end up at the Low Countries), but you get over 500 more Prestige by waiting to the last turn (instead of getting the Decisive Victory). It is a quirk that I've noted to the developers and hopefully will be addressed (you really should get more Prestige for a DV over a MV). So, when I started Low Countries, my Prestige was at 2681 and was just enough to do all my purchases and upgrades shown above. If you get the DV, then you'll start LC with 500 less Prestige and have to make some tough choices.
I don't know for certain if you get more prestige for a MV now as its been a few years and patches but it'd be easy enough to check
