Mick, the catch and the fair or foul call was not yours to make. Your partner should have busted up the line (15 feet was probably not enough) to see the play - especially given the game situation. This was an important play and therefore an important call.
Given that there were two outs, tag-ups were not important. But if there were less outs you should have been lining up to help with tag-ups at all the bases - 2nd and 1st would be easy to see. 3rd would be a challenge but most likely the one to be protested.
This is a difficult one - several defensive players running to make the catch, a coach, a runner on first - there are loads of obstacles to see around. If F4 can move 50 to 60 feet to attempt a catch, I can move 30-40 feet up the line carrying all my gear. I would have to have been in the situation to pick the appropriate positioning but would also suggest getting about 10 feet into foul territory and creating an angle from outside all these players trying to make the catch. This might allow a better view.
A third umpire was needed. It was good that the coach was understanding - but even the nicest most considerate guys don't always see things the same way I do.
Sounds like an exciting game to have worked.