I have used LauncherPro in the past and it has been a great app. I will probably start using it again, but I think that the stock launcher shouldn't be getting force closed, and things like one app needlessly taking up so much RAM doesn't help.
FWIW, I have found that LauncherPro is one of the worst for avoiding launcher restarts. If you do switch to LP (or LP+), keep that in mind if it keeps happening, and think about using a different launcher.
Also, of course, the more widgets that you use, the more likely that the launcher will be marked inactive. If you do have a lot of launcher restarts, it may be worthwhile to start taking off widgets to see if losing one or two of them helps with this.
Facebook takes up about 16 MB of RAM on my phone most of the time. If I actually activate the app and then go in to check RAM usage, it goes up to 37 MB. I agree that it's kind of a crappy app. There is the Moto Social Networking app that can include Facebook updates - that may be better for you. Tweetdeck can also show updated wall postings, etc. And, of course, the Facebook mobile web site isn't terrible.