Yes I’d stay airside as you’d need to hit T5 conformance at T-35 for JER so that gives you 55 mins to get from gate to security. Miss a train and you’ve got 10-15 min wait for the next one which is dead time and eats into that 55 mins.

There would also be a bit more flexibility if you approached flight connections at say T-30 whereas get to TFW at T-30 and it’s almost certain to be computer says no.