Lead paint test swabs are cheap and very easy to use - even for a novice. Buy them at any home improvement store.

Not shady if it’s true.

The colder it is outside, the lower the humidity needs to be inside to stay above the dew point and avoid condensation. Basic whole house humidifiers just have a % humidity setting which can cause problems when temperatures fall as you mentioned. There are nicer controllers that also measure outside air temperature and automatically reduce humidity when it gets colder outside. Talk to your HVAC professional about this.

Servpro won’t flood cut the wall unless it’s necessary. The most common reason for this is that there is wet insulation or some other moisture barrier in the wall that won’t dry fast enough to prevent mold growth. If it’s not necessary they will dry it in place.