A PSA of 43 is certainly higher than it should be, but it's honestly not very high. If your Dad had advanced cancer (incurable cancer that had spread outside the prostate) a PSA score in the hundreds or thousands would be typical. The highest PSA score I can recall being reported here was 13,000. There are many conditions that can result in an elevated PSA.
Don't make any assumptions or assume the worst - just wait for the diagnostic procedures to be completed. Your Dad very likely does have prostate cancer simply because the vast majority of men his age do; it's just a part of the aging process for a man. That does not mean that it requires treatment or, if it does, that he can't be treated with curative intent. Most men die with prostate cancer, not from it. I know that waiting for results is difficult, but that's honestly all you can do.
All the best,
Chris