Lepto = no! At least I don't think it's necessary and has way too many risks. Jackson, who is significantly bigger than your pup (he was 6lbs at 12 weeks old, now is 15lbs) had a reaction to it, so it's not just the tinies who react badly. He got lethargic and starting vomiting, shaking all over, could barely walk. It was terrible to see.
Not every dog has this reaction, but to me it's unnecessary to risk it really, unless lepto is really high in your area or something.
Rabies, by law, is usually required by (I think?) around 4 months old. However, I held off. I was sooo scared by his reaction to the lepto that I was scared to give him more shots, lol. Jackson was around 6 months old (and 10lbs by this point) when I gave him rabies and he was totally fine.
He was outdoors alot too.