Why am I splitting at the seems?

I’m using the file that was supplied with the course that already had a bevel and subdivision modifier applied to them. All I did was add a displacement node to it. It looks like it’s already using generated coordinates by default. Using different mappings doesn’t appear to help fix it. No transparency or anything. 

These are the modifier settings:

I made it as simple as possible with this node setup and result:

All that said, this is more of a secondary problem that only shows up here. My main issue that I am currently struggling with is figuring out the map range better. I would like it to take the “from” range and just scale it to the “to” range basically normalizing the output so that I can use the same “to min and to max” on different map range nodes to make mixing easier. The problem I have is that I go to mix in another noise texture, and one doesn’t show at all because it’s range is too small compared to the other input, or the opposite, it’s all that shows because it’s too big compared to the other. Then I’m stuck trying to mess with the values and everything gets messed up. Then adding a third one in means I have to mess with all of them again. I guess I could just use a strategy for tackling using mix nodes with map range nodes.