Re: Pear Tree Pruning
There is nothing wrong with pruning fruit trees to an open center. It is now primarily done with peach trees, whereas apple and pear are trained/pruned to a central leader. The vertical sucker growth is pretty normal.
Continue to thin out/prune any growth growing up, down, or in to the center no matter the age. If it's an older tree and it is at its mature height, you are mainly pruning to maintain and shape the tree. If it 5 or so years or younger, reduce any new growth by 30% or so, and prune to an outward facing leaf bud.
If you have excessive sucker growth, there are a few things to do to reduce it. You can try to do less heading cuts as this tends to stimulate vertical growth on that branch. Second, hold off on any fertilizer right after pruning. Third, do some pruning in the summer. Winter pruning encourages growth; light summer pruning discourages growth.
I would recommend Penn State's home orchard guide. You can find it online or buy a copy. It's a really cool book and it will help you, I promise. Good luck with your pears.