Why do dogs pee on anything upright? Tree, fire hydrant etc?
Standard water heaters in the US come with 3/4 pipe thread fitings, so 3/4 is what you need. Most plumbers tend to use a torch and solder MPT adapters onto straight copper pipe, but there are fittings that are supposed to make the job easier. There are several reasons why your fitting may not work: 1. the threads on your original fitting might be stripped, preventing the new fitting from getting a good seal. 2. you could be getting a different type of pipe thread from the store. 3. you could be overtightening the fitting when you put it together, One solderless solution might be to use a new product called shark bites. You don't have to solder them, they wokr like a compression fitting, but they go together like ridgid copper. (take a look at the attachment)
I am a little confused about your questions Please open the door with the company and see if he was fired for just attendance or a combination of things, If he can prove that his attendance was not the problem you have a case for a suit against the company. I don't think that face-book or other social networks can be used in this fashion. My best advice is to contact a lawyer and see what they have to said on this matter. Good Luck
Cut the pipe that is leaking about 6 either way from the leak. use a pipe cutter so you will have a nice clean cut. You will be replacing about 1 foot of pipe. Get the proper size pipe and two collars. Mark the pipe one half the distance of the collar so the collar will be centered. Install the new pipe and collars and solder them back together. When you heat the pipe to solder the new one in heat the pipe and not the collar. When the pipe and collar are hot enough it will accept the solder. If you don't know how to solder you can buy compression fittings and use a wrench. Soldering is not that hard to do.