I agree that you are right regarding the "Dutch drop" being done after the passengers were unloaded. Should have realized that one. But I beg to differ on the Train three becoming Train 4. What happened to the locomotive and cars of train No. 1? That's the 10:10 AM Train 4, IMHO.
Train No. 2 runs from Bridgton to Harrison, turns and becomes No. 1.
No. 1 runs from Harrison to the Jct., turns and becomes No. 4.
No. 4 runs from the Jct. to Harrison, turns and becomes No. 5.
No. 5 runs from Harrison to Bridgton and ties up.
No. 3 runs from Harrison to the Jct., turns and becomes No. 6.
No. 6 runs from the Jct. to Harrison, turns and becomes No. 7.
No. 7 runs from Harrison to the Jct., turns and becomes No. 8.
No. 8 run from the Jct. to Harrison and ties up.
That's the only way the times work out for crews. Other wise you have one crew only working four hours and another crew working well over 16, unless you assume a third train out on the line. Remember there were only four engines on the road at that time and with necessary repairs that would strain the motive power week in and week out.
This schedule allows the north end freight activities arround Bridgton to be handled by a locomotive out of the Bridgton shops or by the crew coming in off of No. 5, since they've only worked about 8 hours at that time. The Jct. switching and sawmill switching on the south end would be handled by Train 1's crew and then by Train 3's crew during their dead time between trains, with tidying up being done by the crew of Nos. 7 and 8.
But it still leaves the question of what was done during that 15 minute overlap?.