I would recommend doing everything in your power to finish the level as quickly as you can. Don't worry too much about trying to earn a lot of money here, there are other things you could do in the game to get that.
To be able to do that, that means getting the money to be able to leave as fast as you can then race to the finish. You'll need to have the right weapon upgrades and you need to be a crack shooter (mouse/keyboard combo is a necessity here if you have the PC version).
Accuracy is very important here as you can build up the multiplier for every kill you make but lose it if you ever miss. I would recommend you come in equipped with any pistol at level 4 with the (optional) akimbo pistols upgrade and use this weapon exclusively for the first half of the level. Akimbo pistols effectively doubles your ammo between reloads so not essential here.
Go for headshots on all the mascots. One shot, one kill. Try to do it as quickly as you can and don't miss! Don't worry too much if you get hit, take your time, you can almost always find a health target nearby, just don't take too much hits. When you have a high enough multiplier, go for the money shots for maximum effect. When you have enough money, go ahead and switch to your strongest weapon (if you are able to earn presents) and go on to the finish.
When you encounter the brutes, it would be better to avoid them and not kill them (especially the first one). As you know, they will respawn endlessly if you do. But don't just try to run past them, you'll need to damage them enough to the point that they cannot move anymore (and you have the choice to finish them off). Once they're in that state, then you can move on past them.
Otherwise, kill anything else in your path to the finish.