Is there any connection between your haemoglobin value and the VO2 max value?
I.e., can Hb be used to, at least partly, predict VO2 max?

My Hb count was, the only time I've checked, 163 g/l. That was a couple of years ago.

Maybe, you also have to account for the heart's volume per pump as well...

and max HR... it is a maximal value after all.

stroke volume x max heart rate x oxygen carrying capacity of blood is proportional to VO2 max. So yes it is one term in the eq. But no in that taking EPO (or blood doping) wont increase your VO2max much. Cardiac output is the biggest limiter.

Really VO2max values are overrated as almost everything is done at submaximal intensities.