I think it can be hard to potty train little dogs because when they ask to go outside, it's easy to miss their signals. I know some people are against potty pads but it sure is easier. That may be too late for your guy.
How about a belly band? Just put it on him when he is in the house running free, and take it off so he can potty outside. I know it's not ideal, but it will save your carpet. I have friends who have little males and they put belly bands on them when visiting other homes. Some little boys just like to leave their mark.
good luck, and I don't blame you for not wanting a baby to crawl on potty carpet.