Lost elect to diningroom, kitchen, & porch?

Well you said you had a lot of changes done though it looks good and also that everything is coming from the same J- box. If you mean that your wires come from your panel to a j-box and then various outlet or lighting i would work from the j-box in both directions to find the problem. With what you wrote i would say it is a wiring or splice problem. depending on where you live i have lots of free time and can look at it for nothing.