Sorry, I do not understand you. typed_ast does not have such features as multiline dump() and CLI. What relation is this have with the --type-comments flag?

As for fitting tree into the terminal width, the current indentation is 3 spaces. Changing it to 2 spaces will not save much horisontal space, and 1-space indentation is not particularly readable.

I do not want to complicate this tiny feature. If you want more control on the output, you can write a small Python script which calls ast.dump() programmatically.