Missing Number does remove the last digit- if it's blocked, it's set to 0, and if it's not blocked, it's "removed", setting the target's HP to the value it would be without it.
The Tower Lord in question is slightly weak to all elements! Running a double-element formula was actually a great move there.
Hard Tower Lords give 200 points plus 25 for each Tower Lord defeated. Also, if you still haven't defeated at least one Tower Lord, a Lord you haven't defeated is guaranteed to show up.
I'll set a certain NPC from "Random movement" to "Stand Still"; that should remove that issue for the most part.