Pear tree problem

I've got a 4 year old pear tree. So far it is only producing about 5 or 6 fruits each year though this year it has now decreased to two !! I have got orange spots on all the leaves and small black creepie crawlies on a lot of the leaves. This could be why the tree is not doing too well.

So, question is: what are the orange spots and what do I do about them for next year? Also, if anyone can answer a pruning question:- is it OK to keep cutting the top of the main stem to encourage it to grow more bushy and keep low rather than growing taller?

Many thanks in advance.