I've resolved at least one of the issues with the AM profile. It seems that there was a station below the frequency I was using that was causing interference, and generating noise into the SDR. I moved up to 1690 Khz and the noise level dropped considerably. The sound improved as well.
Unfortunately, in the AM mode, the SDR does not like unmodulated carrier. I've mentioned this before, but it appears to act like AGC is on (when it isn't) and raises the noise level. I still haven't found a solution to that, so I may have to go into the code. Not looking forward to that.
And also unfortunately, the Sony AM Stereo receiver I was going to use to listen only goes to 1610 Khz. I had tossed around the idea of potentially getting one of those CQUAM kit transmitters on e-bay, but they're not legal to use here in Canada. There was some verbiage in the latest draft RSS210 rules to allow homemade transmitters, potentially opening the door to kits, but it got taken out for the final revision.