I can only help with question 3 with any certainty. I can add something to the "anything else" too. I bought pre-mixed shellac.
I absolutely feel that it is worth doing a second coat. Technically it may reactivate the first coat a little... but the reactivation takes time, and if the first layer is dry, the second layer doesn't mess with it too much, and then dries with a thicker finish that will stand up to wear and tear better than a single coat.
Then, I would personally say stay away from dyed shellac because of one experience that may or may not be related to the dye. I've used shellac for quite a few wood projects. I would always buy the pre-mixed without dye and I would work on the project... set my brush aside and let it dry. Then the next project would come along, and I would put the brush in the can, and let it soak for 30-60 minutes, which would soften he brush up and let me do my next project. However, one time they were out of what I normally got, and I found another product by the same company that said all the same stuff... except it had color. When I did the same thing with my brush, it dried hard, and I went to soak it for about 30 minutes. It had not softened at all. I let it soak another hour, still no softening at all. I ended up leaving it soaking for probably 5 hours and it never softened. I ended up having to get a different brush. So I now avoid any dyed shellac. Your mileage may vary.