1/ Right now, if you select "No A/C", we still include the cost+emissions of cooling from the heat pump. It's on the backlog to add a "heat vs. heat only" comparison. In part, we're assuming that if you have cooling capability, you'll probably use it (and therefore wanted to include that in the emissions impact), but also that homes without A/C today will have small cooling loads to begin with, so it wouldn't change the answer too dramatically. For now, I'd suggest looking at the monthly costs in the summer on the bar chart and mentally adjusting the headline number for those. Sorry that's not smoother!
2/ Natural gas is indeed way cheaper here -- dramatically so this year, but previously as well. The backtest shown on the site is Feb '21 to Feb '22 -- natural gas prices this coming winter are bound to be much higher than they were last year, so savings numbers will definitely change going forward. It's on our list to (a) make that dynamic clearer on the site, and (b) explore a more forward-looking savings number. Right now, the annual energy costs are "what you would have saved _last year_ vs. your existing equipment", instead of what you might expect, thinking that would be more convincing / less controversial, albeit potentially conservative.
Thrilled to hear you're 6mo into life with a heat pump! Is it air-to-water and still using water/steam radiators, or forced air now?