Sauce – Beurre Blanc and Beurre Monte difference

Unless there was sugar in your cream, there's nothing particularly sweet about this combination. Did you salt the pasta water to roughly seawater saltiness? If not, did you adjust salt before serving? If your pasta water was under-salted, that would explain the sweetness, since the only significant source of salt otherwise was the parmesan.

Heavy cream is equivalent to 36-40% whipping cream.

In the event that your cream was pre-sweetened, there's not much you could do except add salt and hope the sugar doesn't overwhelm. It's a fairly common technique to add sugar to a salty dish to make it taste richer, or salt to a sweet dish for a similar purpose. But it wouldn't work very well if the cream was very sweet. Since I've never seen sweetened whipped cream except in aerosol dispensers, I can't say for sure.

As far as I know, pouring hot stuffs into the meringue (beaten egg-white) while mixing will denature the protein, and thus stiffen and stabilize the meringue. However, I have no idea why you should pour and wait, then mix in.