Glad you worked out a better solution for getting clean urine. I've heard putting it on your dashboard with the defrost is another great method of ensuring the sample will stay the correct temperature. So you shouldn't have any worries there.

Yes, at some test labs they will listen in on you while you urinate. Although this is more associated with probation, I wouldn't chance it by making loud noises while making the transfer, thus, why an actual piss will do the trick for masking the sneakiness you're about to unleash. Since you're also going in with the dilution method as a backup, you should have no problem producing enough background noise.

Microwaving it will do no harm to the the sample, but using hot water or coffee are also great alternatives. You can't go wrong either way, and honestly like you said if you're keeping in your "gouch" it should remain the appropriate temperature regardless if you're measuring it.

Most of all, practice and show confidence! You got this. No worries.