You can run a good marathon off of long singles and a working man's time schedule. What I would suggest to make this schedule marathon specific...
1) Turn that Wednesday long run into a specific long run or progression long run. I'd suggest alternating a hard week with an easy week. So one week you do your normal 2hr 30min at 4'30/km, the next week you run it hard. You could do a straight progression for 2'30 where you go something like 45min easy, 45min moderate, 45min marathon effort, 15min faster than marathon effort. Or just run 2hr to 2hr 30mins pretty moderately hard the whole time (think just taking a little bit of gas off of marathon effort). Or first 90mins steady, then 45mins at marathon pace. Etc...
2) Alternate intervals with tempo or fartlek running for the Saturday workout. So one week is 8-12km worth of intervals (800m up to 2k reps); then the next week is 10-20km worth of tempo / fartlek running (depending on the length you can hover around marathon effort +/- 5sec/km. 400m reps won't be very useful; but I can suggest adding easy 200m reps to the end of interval workouts to work on efficiency. That type of work is always helpful.
3) Don't be afraid to vary paces on easy days. It's great that you have the patience and mental strength to know when to back off and run slow -- but don't let that prevent you from turning an easy day into an unplanned "run to the barn" when you are feeling great. Long, moderately paced runs that leave you feeling invigorated (but not wiped out) afterwards are bread and butter for the marathon.
What that will look like is alternating weeks that look something like these examples:
Monday - 1 hr 45mins
Tuesday - 1hr 15mins
Wednesday - 2hr 30min with last 45mins at marathon effort
Thursday - 1hr 15mins
Friday - 1 hr 45mins
Saturday - 30min Warm up + 10x1000m + 30min cool down
Sunday - Rest
Monday - 1 hr 45mins
Tuesday - 1hr 15mins
Wednesday - 2hr 30min easy/steady
Thursday - 1hr 15mins
Friday - 1 hr 45mins
Saturday - 30min Warm up + 16k starting at MP + 5sec/km, progressing to MP - 5s/km + 30min cool down
Sunday - Rest