

It depends on your overall energy use but generally that would be negligible when compared to heating and hot water, especially during winter when the furnace runs 24/7.
In particular, during the winter, all excess energy from the oven is heat the furnace doesn’t have to provide so it’s basically free: you’d use that energy anyway.
Generally the economy of scale should technically favor the prebaked bread, at least before the store slaps its value added surcharge for it. The store still needs to pay for the energy (but probably gets it cheaper than you), but also needs to pay to maintain a factory, equipment, employees. So you kinda need to factor in the price of your oven too and its wear and tear.
I just buy the loaf because one thing I know for sure is if I factor in the value of my time, it’s way better and easier to work an hour than spend an hour baking a loaf of bread. The time to bake the bread costs more than if I used that time to work the equivalent time and buy 5 loaves of bread with the money.
The email used to be used to send you notices if your cert wasn’t renewed and other communications. They’ve just discontinued that feature, so the email isn’t super important.
It’s a good idea to provide a valid email address, but it’s not that important and doesn’t really matter for the purpose of issuing a certificate. It’s not part of the problem you’re having.