There are many threads on this subject if you use the search function.
It appears that you have forgotten what the FAF altitude is for.....to check that you are on the correct glideslope? If you choose to disregard the temperature correction then you have not done so and may become another statistic.
As a matter of course, having checked your flight manuals, you may find that managed (LNAV/VNAV) non-precision coupled approaches may not be used in temperatures less than 0C.
It appears that you say you can apply the corrections only if you wish to? I'm sure your Ops manual will not give you that wording.