Hor. Sat. II. vii. lines 40-42. Need help on "quod"

Context: Davus a slave, given permission to speak, is pointing to some inconsistencies of Horace, by quoting the imagined criticism of an acquaintance of Horace.

tu cum sis quod ego et fortassis et fortassis nequior, ultro
insectere velut melior verbisque decoris
obvolvas vitium?

Translation:

While you are no better and maybe worse, wantonly
do you strafe me as if you’re better, and you cover up with respectable words
your own vice?

quod: I can’t parse this.
ego: ditto.

I am guessing that a longer from would be: tu … sis quod ego sim:

Question mark: this tells me that the sentence is a question, but how did the editor know this?

I am guessing that a longer from would be: tu … sis quod ego sim:

Yes, you’re right, but the understood word would probably be sum, not sim.

tu cum sis quod ego [sum] et fortassis [sis] nequior

“when/although/seeing how you are what I am and maybe worse”

The “deliberative” subjunctives insectere and obvolvas mark this as a question: "are you to gratuitously pursue/criticize me and disguise your own fault with [hypocritically] respectable words?

Note the emphatic, almost insolent, position of tu. He could have written cum sis tu quod ego or cum tu sis quod ego.

Thanks Hylander for the tip on deliberative subjunctive. Your comments always help me find the topics in A&G.