is there any fiber that can be added to the heel of the sock as you knit to strengthen it?
Of course it's OKYou only have to worry about gauge when you're following a pattern that has to fit correctlyLot's of people knit tightlyI don't know what you mean by 'short' yarn, though.
If you are happy with your knitting the way it is then do it that way its your knjtting and your choice.
It's your knittingYou can make it how you want.
Many sock yarns have nylon in the fiber, to help reinforce the sockThey are definitely sturdier than all woolAnd there is a way to knit the heel, slipping every other stitch on the knit side, that also helps reinforce the heelI think adding another yarn to the heel may affect its bulk, making it difficult to fit into shoes.
