Ok! here is the first issue I found.
on start destroy all (items) House, Road and Well blocks.
as on creation of house set move to wellblock = run off screen.
set pathfinding cost to canvas or area blocks so that road is less resistance, so that house moves along road before canvas unless no road is created.
edit 1: This would be if you where to use area blocks to cover the play area.
on click
for each areablock (destroy area block) and create item house, road or well
if area block = solid = no path unless you create road.
area blocks can be set to invisible and only you would know they are there.
think of it like dig dug where you had to dig a path to get to a location.
thus also like enemies crossing the un-dug areas pathfinding cost = higher and bug out areas = no cost.
edit 2: also you would have to disable move at angles and use snap to grid as if you create house between grids there would be overlapping issues with move along path. I noticed this issue when creating my point and click demo as path finding area needs to be set to 2-5,2-5 smaller then the block size to move freely along path.
edit 3: it's not perfect but here is a mod of your file
https://www.dropbox.com/s/vs6g34gqdq0bt ... .capx?dl=0