Spaying is the best solution, but you know that.
Local shelters often have programs for reduced-price/free spays for folks that can't afford it.
Feed her kitten food while she's pregnant. Her poor uterine contraction could be a mineral deficiency.
Black cohosh and cotton root bark are both good for opening the cervix and promoting labor.
A cat would get bout .1 to .2 cc tincture in the very back of the mouth.
What are the cats eating, and are Wendel and Shadow related?
Why can't she be fixed?