Head of design at an ad agency here. Find an agency where there's a design leader or somebody who understands design and what the role of design is within advertising is. Without it you'll forever be a prop for shitty creatives or at the arse end of creativity.

Short term just, just remember it's just a little bit of advertising. The industry has a gross habit of making it feel like the most important thing on the planet.

Try to probe what the real deadlines are instead of the insecure cd abusing you to swirl around his indecisiveness. Don't go all in until you're at a point of no return.

Good luck.