这是一个并列句。前句是虚拟,他本可以完成他的大学教育,但事实上没有;后句是陈述说明真实情况,他不得不辞职去找一份工作来养家。这句话可以改为含虚拟条件句的复合句:
He would have finished his college education if he had not quitted and found a job to support his family.
He would have finished his college education had he not quitted and found a job to support his family.