Do you have a picture of a DVD of the scan? A girl is three clear lines and a boy is, well, you know... If you can see it on the screen/pic, that's probably the clearest indication.

As for the other signs... My mum had three pgs, third one completely different and she was sure it was a boy. She has three girls. My ob said the heart rate thing is not right at all, or else he's delivered a lot of babies that had their gender mixed up. It's more to do with physical things at the time of measurement, ie resting, awake, Mum resting/awake, natural heart rate, etc.

Not to scuttle your hopes, but just putting it out there. The scan is the most accurate way until you meet bub.