Building codes require that at the minimum, at least one window in each room be operable. If your windows were painted shut, you were in violation of the building and fire codes.
Unsticking painted windows does not take two and a half months to repair! Your legal responsibility was to hire someone to do the repair, be there to allow access and inspect the completed work. The tenant has no responsibility to open the door for the contractors, that's the landlords job. You should have made sure that the windows were operable before the tenant ever moved in.