At a rough guess from what you've told me (and with a little help from RW), I'd say your paces should be as follows (expressed as min/mile):
Easy (Recovery pace): 8:30
Slow/Base training pace: 8:00
Marathon (Steady): 7:40
1/2M (Brisk/tempo run pace): 7:00
10K: 6:30
5K: 6:15
Mile: 5:40-6:00
Your interval pace (again at a guess) should be between 6:30 and 6:15 depending on the distance covered, faster for 400m (93-98 secs.), slower for 1 mile reps (6:22-6:37).
I'd say you can probably do a bit better than this already (by about 10 secs. even), but it's probably better to start conservatively and work up. You'll quickly get a feel for how much pace you can add, and of course you'll start getting quicker as your training progresses, so just plus everything up a bit accordingly.
As well as intervals, make sure you do plenty of tempo runs, as these are pretty key for the marathon distance.
And try adding one more long run of around 20 miles, following Bruce Tulloh's recommendation that your five longest runs should add up to 100 miles. You'll find that will really make the difference to busting through that dreaded wall on the day.
I'd also say if your running in April and your a RW subscriber, you can do a lot worse than follow the schedules they print from February onwards for the FLM. For my money, they're far more precise (and fun to do) than anything else I've yet seen. Too many marathon schedules just give mileages and don't give enough information about how fast to run them, and frankly these are a waste of time and energy in my book.
best of luck. s.