Lump does burn hotter than briquettes. You might try the same experiment with some K-Blue, Minon method. I don't have a UDS but use a WSM. Big difference in fuel temps. Also go for the tightest air seal possible. That way, all or most air is controlled by you at the vents.
The Maverick ET 732 is a Mighty thing at a good price.
ps: Your burnt offering looked a lot better than my 1st one.