Hi @mhotchin,
You should get a much, much better repeatability than 2mm on re-homing.
There are a number of threads on this topic, it depends on a number of things, but basically you should be able to get a repeatability that is down to fractions of a mm, I know I do. There is probably something mechanical that can be adjusted.
Ensuring equal tension on Y belts (on a properly squared machine) is important indeed, check out this great thread from @LiamN for how to ensure that:
I now use the Gates app and pitch measurement method, works like a charm.
The other trick that comes back regularly to maximize homing repeatability, is this one:
This ensures that the motors lock in place (and the pulleys engage with the belts) in a very repeatable fashion.