Note: If you put it on your resume, then expect a prospective employer to ask you about it. Be prepared to give a careful response if they ask why you left. My advice would be to frame your answer in terms of the positives - e.g. "I did the work they were asking, but it became clear that I wasn't building my skills any further by being there, so I left to pursue other opportunities to learn and take my development skills to the next level." (That is, I probably wouldn't say "The company didn't know what they were doing and they were taking advantage of me, and I couldn't stand it anymore.")

When recommending better keyboards and extra monitors for the rest of the department, the boss may initially see that as an extra expense that isn't in the budget and shoot it down. To avoid this visceral reaction, I would put it in terms of ROI. ("Using better hardware would allow the department to complete X additional drawings per week, so the company can increase sales. The equipment will pay for itself in a couple months and increase revenue in the long run.")

If you're going to thumbs-down my answer, could you please provide some constructive feedback as to how it could be improved or why you don't think it's a good approach? Thanks!

This completely neglects any sense of which tasks management considers to be most important. When an employee has too much on their plate, it's management's job to decide what's mission-critical and what you should let slide.

I agree with @DonQuiKong. Others may or may not bother to look into it. But it sounds like mentioning where the bug was will probably make it clear that it was something he did, not you. But I also agree with the other comments that the management/stakeholders will be more impressed by that fact that you put in the extra time to get it fixed than by whose fault it was.

This is a good way to avoid any unnecessary conflict, but doesn't address the apparent underlying problem - the manager doesn't respect OP or her stuff.