Aw welcome to YT. Your gunna love it here. There is so much information. Congratulations on your baby.
I use frontline on my babies and I haven't seen 1 flea on them and I know they are out there. Some say they wait 6 weeks or so, but I put it on them every 4 weeks. Coco and Pebbles share one vile and Trixie gets her own. I haven't treated my yard either because mine are goats too!!
I have heard that it is not uncommon for the area where they got the shot to be raised a bit but none of mine had this issue. I'm sure there is someone here who has more experience with these little boogers and could let you know.
Welcome to yorkie talk. Be careful though it is addicting here.
Enjoy your baby they are amazing little creatures. Would love to see some pictures of him. Sounds like you are doing everything right. He is a smart little cookie.