Many nutrients many plants need to grow up strong and healthy are not very readily available to plants if the soil pH is not in the range they prefer so those plants grow up sickly and prone to plant disease and insect pests. Since it is relatively inexpensive to adjust a soils pH, although it needs to be dome some months in advance of seeding that crop, that should be done.

Pretty much. I don't personally grow alfalfa, but every surrounding farmer does- it and corn are the premier feeds for dairy.
We have a similar pH. Sometimes the lime is sprayed by contractor vs. the farmer's granular application.
Alfalfa gives 3-4 cuttings for typically three years, some do five. Then a good manuring prior to corn or tobacco.