ok so I'll run you through my process when I homebrew baddies... I start with Final CR first, that's 2. Then decide the OCR/DCR based on the baddie, for now, we'll say 2-2 for about an even offensive cpaabilty and toughness. Next, I like to figure out the HP and AC from there.
At DCR 2, you'll want 86-100 HP if your AC is 13.