Momiji was about 2.5lb when she got spayed. (maybe even less....)
She did good but my vet originally wanted to wait until she was 3lb but it seems she may not reach 3lb for a long time so we went ahead spay her.
She was up and back to her usual self in couple of days.
Please just talk to your vet and when you feel comfortable, do the surgery.
You can never be too careful with our baby!!!