Headshots are key in UDF. Seriously. Otherwise you just waste ammo, which is already scarce. Prepare yourself with the best weapons wherever possible, making sure you always know what's next. Crushing was torture the first time through for me, but after you figure out the easiest way to work through each battle it becomes easier. Plus you usually get a checkpoint halfway through each battle as well.
Which chapter are you stuck on now?
You can do it Goldhawk!!!
At least in SP you don't have to deal with BS lag deaths, which I know are a favorite of yours 
As for your question, I have completed it on all difficulties but haven't platted it because of the dam treasures. I ONLY NEED 3 MORE!!!! Plus I got find out where the HELL the strange relic is. Am too much of a traditionalist gamer to cheat and look it up on Yotube. That be like playing Portal 2, and looking up how to do each Test Chamber. So please, no replies telling me where the things are. 
It's not so stressful knowing you already have Plat. 
