it wasn't exactly realistic but i really liked the NY/NJ war plot line, i thought it was entertaining and i don't think it was much more unrealistic than anything else in the show. pretty much any given point of any season can have holes picked in it if you look hard enough.

i don't think it jumped the shark at all, i just think OP is overthinking that particualar part of the storyline a bit too much. apply that level of scrutiny to any other part of the show and the whole thing falls apart imo.

that said, i agree with lou_para and jace in that the absolute worst parts of the show were the dream sequences and the carmella/furio bullshit (although, aside from the carmella crap fuuuuuurio was one of my favorite characters)