Canning temperatures

[Pro Novice]

I have been successful this year in producing 3-1/2 gallons of liquid gold (up from 3 gallons on my inaugural year last year) on my block arch / 7 tree tap bucket system. I have encountered niter in my syrup this year in my jars of which I had none last year. I have read to let settle and pour off top leaving niter at bottom and then re-package. I have 3 question pertaining to these suggestions:

1) Do I reheat or re-boil top of batch syrup prior to canning? At what temperature should I process this to can and should I re-filter?
2) Do I assume that I take the syrup contaminated with niter and re-boil to density (I use a hydrometer) re-filter and can?
3) At what temperature does niter begin to occur?

I have found this hobby / obsession to be quite enjoyable not to mention, DELICIOUS! I often times think back to the early inhabitants doing this using hot rocks to boil the syrup. And we think that what we are doing is work?!!!

[DrTimPerkins]

Niter will form when the temperature of the syrup goes above 190 deg F. Pour off any syrup you can without letting any niter out. Reheat the syrup to 185 deg F (slowly, best done in a water bath....if you can't do that, heat slowly and gently and stir frequently to avoid hot spots where niter will form). Pour hot syrup into jars and seal.

If you put the syrup into small glass jars, preheat the jars in a hot water bath. Otherwise the syrup will cool quickly and you won't achieve a good hot-pack.

For the syrup in the bottom with niter, reheat and refilter as best you can.