1. I am not sure what you mean by not fitting in the isometric view. The view can be zoomed, rotated and shifted. I believe that the earliest part of the tutorial deals with this.
2. Do you mean signs or signals? In Simutrans, they are not identical - a sign is static, whereas a signal responds to vehicle movements. Also, signs are usable on a variety of way types, whereas signals (other than traffic lights, which are in a category of their own) are usable only on rail based ways. There is no specific tutorial for creating signs or signals: the process for creating the graphics is the the same as for the vehicles, except that only four rotations are needed rather than eight.
3. I do not understand the question, I am afraid. Can you elaborate?
4. The model should be in the Pak128.Britain .blends repository, which is linked in the Pak128.Britain forum.