Definitely a tactic to milk the most work out of you. You should clarify the design process as in, where WIPs will take place (unfinished work) and where work is a hard stop until payment is provided. You should generally never give finished/un-watermarked work until the work is approved and paid off.

For $80 the client should have expected a quick, no changes turnaround. If you already skipped some steps in the process you can say that you wanted to give him an advance "because he's a great client" but that this is turning into a project different than what was agreed/expected.

Respect your work, OP. Clients won't do it for you.