It's not a problem if you don't bleed. Maybe you are absorbing more vaginally, but it is a bit risky lowering your utrogestan dose. I'd give it another couple of months and see if you bleed, as it may be that your own cycle has changed underneath the hrt one. If you are going to lower the utrogestan dose you'll need regular lining scans to make sure it isn't getting too thick, which you would need to pay for as NHS wont do routine scans like that.
Re the resting hr, mine always increases in the luteal phase, even before i started hrt, I think that is just the progesterone. Is it making it hard to exercise? And does it go down again when you stop taking the progesterone?