No problem!

Yes, if your document resolution is 300ppi, then you are reducing the maximum print size because you are using more pixels on paper in one inch worth of space. Frankly, I don’t see that much of a difference in print quality if you print at 240ppi, vs 300ppi.

Same rule applies: 2592px / 300ppi = 8.64" instead of 10.8" (document height).

You can even print at 200ppi. You'll get a bigger print size (12.9" height) but your document sharpness will be reduced, and you'll have to view it a bit further away for that to be acceptable. Look at a billboard. Those are typically printed at 10-15ppi. Stand up close to it, and you'll just see a bunch of giant dots, but at a typical viewing distance, they look normal. You can print your 40D image up to 288 inches-wide at 15ppi, but you must stand 200 yards away from it for the image to appear sharp.

I'm not sure about your saving RAW to JPG issue. Which application are you using when you try to save?