Matise was 4 months when we got him and weighed 2 lbs. He just turned 1 on Aug. 16 and weighs 3 lbs.
1. Potty training - Matise holds it too at night but during the day he is the same. I think it is because they are up and playing, etc.
2. Leash - I didn't have any problem, go for it, just use lots of positive reinforcement. i did use a harness.
3. Food - i feed 3 times a day breakfast 8am, lunch1:30pm, dinner6-8pm. I think that is better so that I know the last time he ate in case he gets sick or whatever. Then I have that info. Plus then I know when he has to poo so i can help with the house training.
4. Weight - not fast very gradual.
5. Sleep - Matise always has slept in the bed, but my husband and I are light sleepers and wake the minute he moves, plus he always sleeps on my chest when i sleep on my back or next to my chest when i sleep on my side.
When I got Matise he wasn't that small but I hope this info helps!