Freed from worrying about the smaller, spellcasting thug, Rever turns and hurls himself at the other, shield and blade both threatening the man.

Spoiler: mechanics
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If I can, I'd like to use the Shield Master shove first -- I'm interested in seeing what the ooze does! If you rule that the Attack has to come before the bonus action, cutting him down is okay too.

First, move to N6.
Shield slam: (d20+11)[13] vs thug 9's opposed Athletics to push him into the ooze, following if necessary to continue the attack
Rapier, Reckless Attack: (d20+8)[17] or (d20+8)[17] for (d8+5)[8] damage plus (d6)[6] Sneak Attack