Did you set the font styles for your layouts?
As a rule of thumb I normally start with a single layout, then set it up as entirely as I can how I want it to look design wise and ensuring all the functionality I will need is there. So I basically setup the design of the navigation and overall looks of a layout in both FORM view and LIST view, then save them as templates. From these templates I make all my layouts for the solution I am working on.
If you follow this method you could use FMs font style commands to set specific fonts, sizes, colors, and styles.
Since your solution is already designed maybe if you apply the font styles to the specific layout you are having trouble with?
EDIT:You will also need to be sure that the fonts you choose are available on both Mac and PC since you are using between both OS's.
Another factor at play here is that text on a windows platform takes up more space than the same text on a mac. You may need to open the file on a windows platform and make adjustments to text size, text object size, and spacing between until they work for the Windows. Since the same text will take up slightly less space on the Mac, your adjusted layouts should now look ok on both platforms.
I thought that was only the case back in the day when Macs had to use Mac monitors and couldn't use PC monitors? These days they both use the same monitors, keyboards, mice, graphics cards, hard disks, USB, processors, RAM, the whole works...?
It's still an issue.