60/day for 4 days will be considerably harder than 50 for one day a week. How much harder depends a lot on terrain and winds. You're right in allowing plenty of time each day to make the mileage. I've found fatigue to be lessened by maintaining a high spin rate, say above 70 rpm. Staying well hydrated and maintaining your blood sugar level is critical. In addition to regular meals, I rely on Snicker bars to stave off bonking. Maybe two or more on a 60 mile ride.

As for nutrition, I try to include a heavy dose of protein in my daily diet. This in the form of peanut butter, cheese, and meat. Post ride each day is often a pasta dish with vegetables and protein. Tuna, chicken, sausage. There is no "recovery" other than a good night's sleep.