You answered your own question on the weight part -- to get the most accurate reading tou weigh after a poop. My snake doesn't always poop every month (even though I observe her tail slowly swell until she decides to go). That's just how she is, and she's growing length-wise and around so I'm not really concerned about it.
I've never seen a poop with fur in it from her-- it's always been a solid mass with one exception lol.
I agree that the size you're feeding her now seems appropriate. I also agree that keeping to a 7 day schedule for now would probably be best. Yours will grow at its own rate, and rushing it won't do any favors.
Very, very pretty, by the way!