You and DH need to get very, very realistic about your wants/needs and your budget.
1. You are NOT going to find a home for under $400K that meets all your criteria.
2. Montessori preschool can cost up to $18000/year at the more well-known ones in NW DC. Can you afford an additional $1500/month?
3. DH will not see his child during the weekday if you live far out with his work schedule.
4. Parking in FB, unless subsidized, is expensive--especially if you want to save for a home. GWU subsidized parking is about $250/mo.
5. If you cannot handle renovations/home repair, consider a condo within walking distance of FB/metro:
http://www.redfin.com/DC/Washington/3001-Veazey-Ter-NW-20008/unit-908/home/40273571
http://www.redfin.com/DC/Washington/4740-Connecticut-Ave-NW-20008/unit-1005/home/9977149
Both are close to Chevy Chase, Franklin, and Auguste Montessori schools. The one on Connecticut also feeds into Murch, which is considered one of the best public elementary schools in DC--which will buy you a few years. The one on Veazey has parking, but feeds into Hearst, which is not as highly regarded as Murch.