Welcome to the world of mixing different softwares.
MyRoute is designed to work completely independently of BaseCamp and now, more particularly, to link seamlessly - with the help of the Garmin Drive app - with modern Garmin GPS devices (like the XT) without the need to go through BaseCamp at all.
The straight lines you are seeing is the result of BaseCamp not having enough data (breadcrumbs) to fill in the gaps between the known shaping or via points.
When you disconnect the device from your PC and then import the route from the device’s memory into the device proper, the device fills in the gaps. When you then reconnect the device to your PC, BaseCamp can then import the fully ‘filled in’ route.
Your second problem was, as I read it, down to nothing more than user error. You asked the device to take you (or start you from) your home address. You were at home but I guess the device thought you were somewhere else, which can happen. It therefore kept on trying to do what it had been told to do….. which was to take you home.
My simple suggestions would be:
Get used to using MyRoute, independently of BaseCamp; they do not need each other.
Learn how to create via / waypoints (as distinct from shaping points) in MyRoute and how to send them successfully to your Garmin device. There is a thread on the topic at the moment.
Maybe refresh your knowledge of how your GPS device works, most of which you are pretty good at. In particular, starting routes. Maybe create a via / waypoint say a mile or so from your start point. On first start up, that point will appear as a possible destination for you to chose. Chose it. No matter where you start from, your device will always take you to that point and then run the rest of the route seamlessly. You’ll only be (potentially) buggered if there is road closure at the point, rendering it inaccessible….. but that is not Garmin’s fault.