助ける is more "rescue." Save it for when you're in trouble. If you just need less desperate help, you would say 手伝える. Either way those are the plain forms, not command forms. 僕を助ける is "You/he/she/it/them help/are helping me." 助けて is actually reasonably polite, but for added politeness you could use 助けてください. The 僕を is pretty much implicit in the command form, but if it's not you who needs help you might say, for example, あの子を助けてください, "Help (save) those children."
Get a hold of yourself!!We do what we can for ourselves!What is Kazami Yuuka to us!?Who will save you if you call out!?Is that so? sou nano ka... Help me.I'm too scared to stand up.Ru... Rumia-chan...This is the only way!!Why are you crouching like that?What will change if you cry!?