What's the point in running 1k then doing a recovery when I can run 10k at 10k pace?! Surely for an interval session, I would run the 1k as hard as I could sustain for 5 reps before cooling down?.
Interval sessions don't need to be flat out. They can have different purposes depending on what you're training for and that session for a marathon is actually a pretty good one (although 200m recovery is too short IMO, I would look at 400 or even 600). If you feel good you could perhaps do the last 1 or 2 approaching 5k pace.
You say you're running a marathon for the first time after shorter distances? You need to look at longer but slower intervals to really build stamina - remember this race is going to take you almost 4 hours, so being able to maintain a solid pace has to be your primary goal. It's a whole different beast to 5k and 10k running.
What's the point in running 1k then doing a recovery when I can run 10k at 10k pace?!
But you can't - not in training anyway. That is of course assuming that is your 10k pace. Even 5k @ 10kp in training is very very difficult. Remember you get adrenalin rushes, competition etc in a race which makes the pace seem easier and allows you to hang in there in the final few k's in a race. I guarantee trying to run 10k @ 10kp (that is your actual 10kp and not an estimated pace) in training will not end well.
Plus, the total mileage for this week (week 4) is only 32 miles? Should I add a few k to each of my runs? 32M doesn't seem very much at this stage.
yes, I'd absolutely add more mileage. 32M for marathon training is not sufficient at all. I'd look at building to 40mpw in the next 4-6 weeks, then in the longer term of 12-16 weeks getting up to 50mpw. If you want to do yourself justice then the base easy mileage is the key - everything else is secondary.