Dropbox has broken embedding, so I had to edit your post to follow your link.
Here’s a picture of the pattern.
It looks like you don’t have a nozzle at all, is that right?
Assuming you were measuring 50mm from the lens with the spacer, now you need to work backward to see where that is coming from.
In our Lasers > Getting Started with CO2 Lasers section, you will find this:
That has one video and two written guides for how to align mirrors. When doing that, you’ll be test firing at tape at each mirror.
Please post pictures directly here (rather than dropbox videos; it’s much easier for us) of the paper or tape at each mirror after the tube, showing the marks made on the paper after exactly one test fire at each mirror.