I had a 8 feet tall semi dwarf D'Anjou that bore fruit. Unfortunately it snapped off at the graft in the wind. D'Angou flavor is extraordinary I miss that tree. Semi dwarf is a loose term. Your tree may top 20 feet. No one knows yet. Some standard pear varieties are 35 feet. I have a 'compact' Lapins cherry over ten feet tall in its second year. You say your trees are 15 feet and have just a few pears. If you cut the tops to 10 feet they will grow back with more little branches up to 15 feet next summer. Heavy fruit bends pear branches way down. Prunning the top will prevent fruiting up there so try tying ropes to the tops to bend down those branches.

For your second question see the thread "Pear Tree" started Wed, 12th just before yours for general advice on determining when to pick Euro pears. I pick my Moonglow here in zone 6a about the third week of August. It's one of the earlier pears.