Let me weigh in with my experience. My surgery was 41 months ago. I am still wonky 24/7...it never goes away, but you get used to it. I am a physical fitness type of person and I still lift weights at age 64...still buff.
But, I have my bad days with fatigue. I have really studied what is going on with me, and I spend all day long just staying vertical. It is almost impossible for me to close my eyes and stay vertical for longer than 30 or 40 seconds. I use my eyes instead of my ears for balance. Staying vertical for most people is easy, just like breathing just happens. If your muscles need more oxygen, your brain tells your lungs to breath deeper and more often.
My brain is telling me you are falling over, and my legs and feet are always trying to keep me vertical. After a full day of doing this, I just feel worn out. Minute to minute it is not a huge effort, but hour after hour, it is fatiguing.
It is not barometric pressure that is causing your rollercoaster...it is your brain...and your first statement was you were having more wonky days. It takes a lot of energy to stay vertical when you are wonky. It might help if you can stay seated most of your day when you are wonky.
Physical fitness is really important. It will help you recover from your procedure and it will help you deal with your fatigue.