Is your Timeline_Dataset randomly selecting time moments on every iteration? If not, your network will only see and predict fifth minute exits.
To “predict for every timestep” you normally don’t use “lookback” (except as limit), feed longer sequences, and rely on RNN’s implicit discarding of older data as “lookback”.
In other words, in your implementation, you should already have 4 timestep predictions, if you stop thinking about 5 minute chunks.