you might find something here:
The Caregiver's Home Companion - Resources ?
if i were in that situation i'd be struggling emotionally. for several reasons. my only suggestion might be to hire someone who will supplement your caregiving. you said you have someone to help during the day, maybe there is someone in your neighborhood who you could pay to take a shift? or find a professional respite care worker?
other sites to try:
Caregiver.com - For caregivers, about caregivers, by caregivers,
Caregiver Support - How to Care for Yourself While Caring for Others,
Preventing Caregiver Burnout: Tips and Support for Family Caregivers,
National Family Caregivers Association (many of these are probably about caring for seniors, but i'd imagine there are similarities.)
good luck! respite care is probably a good option, they may offer later shifts as well (or weekends).