Steve A, Now that I see the diagram, I understand why you steered to port. I think I would have too, and then slowed as the head-on boat approached at speed. Sorry if I was rude in my first reply. You basically dealt with one problem at a time, and I think that's usually the best approach. That's a dicey area to boat. Won't be surprised (but I will be disappointed) if they make the whole area a no-wake some day.
The 34 foot boat's captain should have throttled up momentarily to clear the area (best choice) or throttled down and let you pass; just to avoid a "situation", even if he/she was not obligated to do so. If it were me, I would have been long gone by the time you arrived at the original point of intercept, I always lean toward throttling up; hard to be in an accident if you are not there
If you failed to slow to headway speed at <150 feet, the MP did the right thing. Glad it was just a loud-hailer warning and not a ticket. I think the 150 foot rule between boats out in the open is kinda silly. MP must've thought so too. Can't say I have ever seen a pontoon boat "pulled over"...