If you understand that his goal is to push you out, you are halfway at the solution.
Now, the obvious response would be early retirement. However, given that you write here, you do not seem to want to retire early.
If remaining until retirement, however, is your goal, the most important thing to protect is your health. You have to ask yourself whether staying for the additional years is going to be worth massive health problems.
However, it need not be an either-or. Basically, once you know that he has the goal of pushing you out, you have to take everything he does as an action to that purpose. So, when he insults you or falsely accuses you, this is not true, this is not even him thinking to be true, or any approximation of what he thinks to be true, but simply a way of making you so uncomfortable that you quit. In other words, do not take it personally, in the most literal sense.
Getting the insight that somebody treats you badly for explicitly tactical reasons can permit you to get an emotional detachment from the bully, because they lose the hook that permits them to control you: you know that he does not throw the accusation because you are in the wrong, and you realise they just throw attacks at you to get you emotionally off-balance. This permits you to put a screen between what they say and your emotions. They make no attempt at an honest expression of dissatisfaction and you shouldn't take it as such.
Realize that we tend to respond to bullies in the way they want, because we aim to keep your standing. However, realise that your standing is not that important, especially coming closer to retirement. Also, it is very costly to maintain, once you have a focused bully who works on destroying it. We attach a high value to standing and try to "be good". However, standing is a social currency, and a capable and committed bully can often turn this currency to be quite worthless and unreliable, without you being able to prevent it. Do a good job nevertheless - this is under your control. Interestingly, bullies often have fine sensors that notice when we decide to drop our internal pressure to maintain standing in the group and we stop caring about it; and losing this "control knob" can weaken and demotivate them and - paradoxically - gain you support with the others in the group. However, committed bullies may be then seeking of novel ways to press your buttons, so never let your guard drop even if they start to relent.
Once these insights are in place, a short list of how to try to survive the next 3 years:
- Protect your health, with highest priority.
- Make sure you have a good network of friends and/or out-of-job activities.
- Do your job well, as well as you can.
- But recognise intimidation as what it is: not an attempt to improve the situation, but to damage your confidence and standing.
- Do a good job, but drop any ambition of maintaining your standing in the department. It's not worth a health investment. Detach.
- Document everything, with time and date.
Good luck.
