You don't have to increase the number of locks when increasing number of open objects ... unless you're also getting messages about having run out of locks (and you've determined that there is no way to reduce the number of required locks).
Use sp_countmetadata to get an idea of the memory needed for a specific 'number of open object/index/database' settings.
As for lock memory usage ... while there may be a blurb in one of the manuals it's probably easier to just find the current memory usage (sp_configure 'number of locks') and multiply this by the same factor by which you plan to multiply the number of locks.
Also, additional memory for the increased config settings (eg, number of open objects, number of locks) comes from the amount of free/unused memory (see last couple lines of output from 'sp_configure memory').