Not sure what this means:
I cannot seem to find the inspector on 'Modify' view when setting this table up.
Do you mean Layout mode? If so, go into layout mode and look in the View menu for "Inspector".
Now, to your problem at hand.
If all new number fields that you add to your layout are set to display as percentages, I suspect that you've inadvertently set this in the inspector as your "default".
Try this: Go into layout mode, and open the inspector. With no layout objects selected, go to the Data tab on the inspector, go down to the bottom where the "Data Formatting" section is. Click the ".01' button for number format. In the popup where it says "Format", change that from "Percent" (which is what I suspect it says now) to "General".
When you set or change settings on the Inspector without any specific layout object selected, those options are considered your defaults for when you add new layout objects. If you were to follow the steps in the previous paragraph, for example, and set the format to "currency" with 2 decimal places, FM would assume that any new layout objects (that are numbers) should be formatted as 2-decimal currency.
Thanks for that Chris, couldn't find it for looking.
Regarding the other point you questioned, when I'm in table mode, I can click Modify to add/remove fields, but cannot use the inspector in this view. Perhaps I have things set up slightly incorrect.