I am so sorry to read about your poor cat,i have cats and they only go in my back garden which is very enclosed, no dog could get in, but did have a cat years ago which was mauled by a visiting alsation, poor thing was never the same, although physically she recovered
I also have a little dog,who is always on a lead outside, but I have 2 neighbours who have dogs never on leads
2 jack Russells and 2 Staffies, I hate taking my dog even out of my gate if they are around,although they do go back to owners when called
I hope your cat recovers, I can imagine what you are going through
Are you going to report this neighbour anyway, I would still report to the dog warden