You and your son will be just fine this school year. As you well know, from many years of homeschooling, one of the advantages of homeschooling is that our children don't have to be at the same grade level for every subject. We can work on their strengths and weaknesses as we go along, at our own pace.
Continue with the seventh grade materials that your son has not completed, and don't feel rushed. You can catch up next summer if you like, or perhaps assign a bit of academics over the weekends. You may also consider teaching only core materials this fall. For example, pass on Art, Writing Workshop and maybe even the Reading Comprehension Volume 4 (those can be read independently at a later date, and you can test your son's comprehension in Science or Church History.
Remember as your son gets closer to high school years that you and he can decide, in the future, when or if he is ready to move on to post graduate studies. It doesn't have to be the day he turns eighteen - but work on the decision together. Of course, pray for guidance.
We all need prayers, but your situation is unique in that you have homeschooled for quite some time, but lost a husband and father. You are also working outside the home. I will pray for you and your son that God will comfort you both, that you both have friends and family to love you, and that you have a wonderful school year together.
Blessings to you and yours,