In my experience you really don't need to worry about changing up your diet for the type of endurance you're looking for. I crossfit twice a week and lift heavy twice a week, my ratios all stay the same I just end up eating more when I'm hungry more. Don't worry about your diet, your body will tell you to eat more as you need it.
For exercise, I don't run at all other than what is included in the regualr crossfit programming, and my 1.5 mile times have steadily improved. I've read articles about a runner training for an ultra marathon using exclusively crossfit and doing well, also doing the same with regular marathons and destroying her old times. Another article about a guy who never ran at all, trained for a half marathon using only crossfit and came in just over 2 hours.
I'm certainly not saying crossfit is the only way to train, but it's been very effective for me, and more importantly, fun. If you are mostly focused on endurance, I would recommend hitting crossfit full on, then give yourself a few days to a week off just before the event, with only some light active recovery work that week. After that, you could add in max effort (heavy lift) days to replace a couple crossfit days a week.
I'm sure there will be plenty of solid advice here, this is what has worked very well for me and I couldn't be happier with it.