I have just found a solution to my issue as I was typing this after inspiration, but it is a work around so wonder if what I have done is the best way.
I've created a project and theme at the size of 1024x768, which is my main project size. I am then creating a smaller project for demo purposes. I import my original theme, not for the background since I convert them all to a white background. What I find out that in a smaller project the colours are correct, etc., but the font has decreased in size. In my example from point 18 to 11. I was wondering if there is a way when importing a theme not to scale font size, etc.?
My workaround is to:
1. Create project at required size.
2. Resize project to 1024x768.
3. Import theme.
4. Resize project back to smaller size, but crop project and don't allowing object rescaling.