Difficult to decipher but this is what you should be doing....and note that when it comes to digital images its the PIXELS that count.....everything else is calculated from them.
Your original document should contain enough pixels to be printed at the size you require.
You should know the resolution you wish to print at, and the size of the print, so the PIXEL dimensions should automatically be calculated for you.
Once you have your document of the sufficient PIXELS you can print it out at virtually ANY size you want...problems arise when there just aren't enough pixels to print at a specific resolution / size.
To VIEW the document AT PRINT SIZE you need to have set the RESOLUTION of your MONITOR in the PS preferences. You'll find this under PREFERENCES > UNITS and RULERS > SCREEN RESOLUTION
Once this is set, using VIEW > PRINT SIZE will DISPLAY the image On Screen at the actual size.
It goes without say that as the name suggests it will also PRINT at this size too.
You need to be reasonably accurate when setting the Screen Resolution for this to be useful.
If you need to know what size your print will be then use the IMAGE SIZE window. With regards to the current Resolution setting the physical size of the print will be displayed.
Regards.
MrToM.