If repairing Office 2010 and applying all the updates doesn't fix the issue then updating to Office 2016 is unlikely to fix it, for if anything Word 2010 makes better use of memory and is faster; and yes you do have to buy/rent the whole of the 2016 product.
Frankly it is difficult to know what the problem is. Have you tried running a memory test -
https://technet.microsoft.com/en-us/...or=-2147217396