is it possible to make my pecan plant stay small?

It can be done. You need a branch cutting and a root graft to a branch. This takes some skill. Best done by a nursery for you. Then you can grow a pecan bush. The fruit will be very small. I would recommend cherry for the blooms. And raise inside as a potted bush. It will get about 4 foot tall. and 4 foot wide. Can be trimmed to a round ball. Needs lots of sun. A pecan is a bush not a tree as well. And should work asa bonsai tree as most all trees can be raised that way. But I have never done one. Just read that most can be done.

Well, first of all, pecans grow on trees not plants. Second, there is no way to force it to stay small. They grow anywhere from 70-100 feet tall, so it won't be anywhere near a "bonsai".