Has anyone had the experience in dealing with their loved one exhibiting superhuman strength?

I do not have experience taking care of someone with that level of dementia, but I would think that a visit to the doctor to get some medication to calm him down is necessary. You could have been hurt or your father too. As to your question about super human strength, yes the body can exhibit tremendous strength when fueled by adrenaline. I witnessed this once with my 4'10", 120 lbs. mother with bipolar when she was in a manic phase. It took 3 burly EMT's to wrestle her into the ambulance. I remember a doctor telling her that these episodes would shorten her life if she didn't take her medicine properly because all that adrenaline was so hard on the body. Well, she is 86 now, but she lost mobility and the ability to take care of herself many years ago.