Also, start daily status reports. Mail them at normal closing time and again after your overtime if you do it. Mark what you got done, what is in process, and what is next up.
When a new task comes in, add it to the list in the proper place. If a running task was bumped to make room for an emergency, that gets an ALL CAPS NOTE marking the change in priority.
Mail these to the boss and BCC them to yourself in a personal account. Keep copies of his replies as well.
At best, the act of mailing these alone should show that you're trying to keep on top of things. It might reveal to the boss how much you have on your plate. At worst, you have a paper trail if it does lead to a constructive dismissal situation.