What are your settings under Tools > Options > System Options > Default Templates and File Locations?
decimal places and fonts and such are DOCUMENT options, so they only apply to the current document. you need to update your drawing template (or make a new one). - start a new drawing, load you document options (called a drafting standard) and then hit save as and choose drawing template as the file type - either overwriting your existing template or make a new one. you can also update the sheet format before saving.
(side note: anything you customize in SW should be saved in a custom location. it will save you grief when you upgrade versions)
In addition to Anna's and Jeremy's reponses, here is a discussion with a great deal of information about working with sheet formats and drawing templates: https://forum.solidworks.com/thread/57204. Reviewing it should help you quite a bit.
To elaborate on your last question, right-click on a blank part of a drawing sheet and choose "Edit sheet format". Make all desired changes. Right-click again and choose "Edit sheet" to exit the function. Next go to File > "Save Sheet Format..." to save it so it will be available to use for future drawings. To default to it when you start a new drawing, open a new drawing, right-click on the tab at the bottom of the sheet, or a blank part of the drawing sheet, and choose "Properties..." That will take you to the dialog box where your new sheet template will be available if you have pointed to the location where you saved it, as Anna asked. Select this sheet format and click the Okay button. Save your drawing template, as Jeremy explained. Some of this may have been stuff you already know, but I didn't want to leave out anything.
Please reply to let us know if this solved your problem.