my post page the excerpts come in from the posts but the background image disappears leaving a white space above the excerpts.
How are you adding background images?
The white space is the slider. It is empty because you have not selected a category. You can turn the slider off on Frontier Options -> Slider
Also are we allowed to have 2 post summary pages on the same website that could display posts of just one different category on each page?
Add category urls on your menu instead of pages. Look at my menu above, I have “Blogging”, “Graphics” and “Random” which are categories that only show their own posts.