The easiest way would be to dig the dormant plant in November, cut back the top, stuff it in a trash bag for the trip, and replant it in the Maine garden as a bare root. Will the ground be frozen Nov. 30? I would guess not in Mass., maybe but probably not in Maine. You could open the hole in advance, prepare the soil, and pile leaves over the dirt pile to keep it from freezing. Late fall planting of bare roots used to be standard procedure in zone 5. Also, mulch heavily around the Mass. plant when cold weather arrives to be sure it will remain diggable. If you transplant to a pot now, it will probably defoliate and use up energy growing new leaves, which would be killed by frosts very soon. Then you have the hassle and risk of overwintering a pot.

wuzoo, you might want to cross-post this on the Garden Clinic Forum. I'm far from certain, but the insects look to me like planthopper larvae. If so, they're sometimes considered more of a nuisance pest than a threat to the tree, and one can do more harm trying to eradicate them than by just letting them run their cycle. You might also check with your local extension service. Sometimes if insect pests make an appearance in unusually large numbers, the ext. service will put out information and recommendations on control and management.

The plant is a Schefflera. The yellow spots look like scale but hard to tell as they are out of focus in picture. I wouldn't want to pretend to be an expert on getting rid of scale but you could do some research on solutions for that.

It's a jade plant, Crassula. Is it near a sunny window? (It should be.) Is the soil constantly moist? (It should not be; let it dry out between waterings.) I have never seen one do that, so I am not sure what the issue is.