How can I remove dried paint from carpet and leather?
Carpet
I'd give up on the carpet and order a replacement.
Leather
The usual techniques for removing paint from leather are to try one of the following treatments in a small inconspicuous unpainted area of leather first to see if it harms the leather (there are a variety of ways leather is made, so results can vary), then try it on the painted leather, keep trying treatments until you find something that works.

vegetable oil (cooking oil)
vaseline (petroleum jelly)
warm soapy water (and a non-scratch scouring pad used gently)
nail polish remover
rubbing alcohol (isopropyl alcohol)

You'll probably need to follow up with some leather conditioner.