You were about 3-4 months early for seeding a northern lawn like fescue. Spring is a poor time to reseed and summer is simply awful. Early fall is the best time to seed...for the reasons you're experiencing.

You can try to keep it alive, but I'm not sure it's worth it. You'll be fighting one issue after another until you've bombarded it with just about everything.

I guess I'll sod the whole thing... I can't let erosion continue until fall.

Or...! Mount a spreader 50 feet over my lawn and drop truckloads of ice in it, to keep the lawn cool and moist.

Last remark... I knew late spring would be tough, but I had o try it. Had the weather been average, I would have succeeded.

It's only 2 1/2 months until September. You can seed as soon as the summer heat starts to break, which could be mid to late August or early September. How much erosion are you expecting in the next two months? You can sod now but it would be better to do that in the early fall too. The summer heat is brutal even on established grass.