The more I get through Paul's various letters, the more i feel that Christianity could fairly be called "Paulism". Anyone else feel the same?

Depends on the denomination. I do feel his influence is generally outsized compared to the other apostles, possibly overwhelmingly so. But since he was the one most focused on converting non-Jews instead of convincing Jews that Jesus was the Messiah, and since those same converts eventually came to greatly outnumber Jewish Christians, it's not exactly surprising.