Good to see Bulk again (how exactly did he get back from Mirinoi?), ...
He probably used a spaceship, interstellar travel in the PR universe is not a big deal. But he has been back on earth for almost a decade, it's not Samurai's job or even necessary to explain it.
I hope the nephew is Skull's and Kimberly's son, they had a lot of chemistry and that they got married has been fanon for years and almost became canon in Wild Force.