This last detail is most important. The cut, where the bridge meets the table will have to be cut at the right angle. I'm not sure what this will have to be, but you can find this out by running a few tests after the main part of the bridge is built and installed. I think that a 10 degree slant off vertical would be enough, but I would want to test this with a mock-up.
The ties next to the join should be replaced with PCB ties. (Printed Circuit Board) and your electrical connections for your tracks can be made through a 6 pole trailer type plug. You know what I mean? One of those black rubber cheap-o 6 pole electrical plugs, that would be very reliable for the numerous plugging in and unpluggings to come. 6 pole, because you have 3 tracks. This should plug in just under the pin you least use. Leave enough slack to make this job easy.
Here is a drawing to illustrate the angle the cut should be.
Using the 4 door hinges will be sufficient to keep your tracks aligned. No other device will be necessary.
Now go build yourself a swing bridge.
TrainClown