Did you actually pack the bearings? I try and fill it up, The shaft takes up a lot of room. Bearing buddies are the way to go. Tongue weight, I think your over thinking it. Trailer should have weight on the tongue when hitched and loaded. If not it will sway like crazy. 200-300#'s you should be able to just lift it. Even 100#'s of tongue weight will work. There's no perfect weight.