Outlets worked intermittently with voltage fluctuations and are now dead entirely
Having no voltage indicated on your meter would indicate a bad connection on the hot wire for most meters (an open neutral would show some voltage with high impeadance meters that are normally used). I would start checking at the last working outlet then the first dead one. When the new outlets or wiring was installed did they use the back stabs on the outlets? Back stabs or push in connections are notorious for failing. Most of the knob and tube replacements I have done the boxes were in the attic, it is very rare for the boxes to be in the crawl space but I did find several on 1 job.
Use caution in the attic because sometimes the in wall knob &amp; tube was left in place but the feeder wires to that junction box was updated (still allowed by code). 
So start at the 2 outlets since they would be the easy ones to get to then start checking the attic junction boxes.