It looks like your B cable is broken?
In a perfect world you should have it. To answer your question, it is not necessary. Just be sure your throttle snaps back to idle. Which it should do whether you have the B cable hooked up or not.
As to the oil filter bolt, this is one of those things that age creates. The bolt is not stuck because it is too tight. it is stuck because a chemical reaction has occurred between the bottom of the flange of the bolt and the filter housing. From exposure to the elements, condensation and road spray. had it been removed once a season, it would not be stuck. If you can grind or drill the flanged part of the bolt off without getting into the housing, you will spare the housing. Once the flange part is off, the housing will pull off and you'll have the length of the bolt to work with. But you'll probably be able to turn it out by hand.