Hi and WELCOME to YT
!!! Your Bella sounds adorable. Answers to your questions:
1. I won't answer this one since I don't use flea meds, but I'd def check w/ your vet
2. I wouldn't worry at all about her getting fat at this stage of life. But on the belly - is she just full or does she actually bloated? You don't want her bloating, as that's very uncomfortable. If it's bloating, I'd be wanting to change foods.
3. I recommend the chloroform
. Kiddin'! It sounds like she gets what we call the "zoomies" in the morning, which I love watching..she's prob just getting some excess energy out. As far as people coming over, you prob do want to address it if she's getting way too excited , otherwise it may turn into a bad adult habit. Maybe try soothing her a bit when new people come over before turning her loose. That said, young puppies are just so excitable and it's part of their socialization to be like that, so you can only control it to a certain extent.