No top dressing needed (ever in my opinion).

I would not reseed in the spring, although you do live so far north that crabgrass might not be a concern. Fall (August for you) is the best time to reseed.

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

So rather than watering the crap out of it, water it properly instead.

Spot spray weeds in April.

Fertilize in mid to late May. Don't jump the gun on fertilizer thinking you can improve it faster. It might improve faster, but that becomes a short term solution leading to collapse in the early summer. It will NEED fertilizer in late spring anyway, but it does not NEED fertilizer in the early spring. If you can't stand it and feel the need to fertilize with something early, use organic fertilizer like soybean meal at 15 pounds per 1,000 square feet. That will do everything you hoped for without depleting the stored energy in the grass roots.