Tricia: My Comrades training schedule says 50 - 60K in week 4 of the 16 week plan, so somewhere around Mid March, so your plan should be OK, personally I never do the first 50K run preferring to run a hard marathon instead. If you want to get in to Comrades enter on 01st November and you will be fine, 1st first come first served.
The mental side of Ultra running? Well you will have bad patches, its learning to get through them and how to ignore pain thats important, I have a couple of coping stratergies,
1 I break the run into sections and only think about getiing to the end of the section I'm currently running,that objective might be a aid station or in the case of comrades the next timing mat. The rest of the run can wait until I get to that objective.
2 Distract myself by trying to name all the english league football teams, counting how many countries I have visited etc etc.
3 If really desperate count my steps, I can assure you by the time you get to 500 you will have forgotton what you were worrying about!