My plan is to have a Viessmann Vitodens 100-W boiler with combi-kit installed and exhausted through my masonry chimney using grey IPEX CPVC piping with insulation around it to protect against Toronto weather.

My questions are:

1) I'm considering having the air intake from the surrounding room instead of a separate air intake pipe to the outside. Would there be any concern of CO backdrafting into my house?

2) There is a TSSA regulation that says I would have to "seal the boiler room" for a Category I gas appliance ( Am I correct in assuming that this does not apply to the Viessmann Vitodens 100-W, regardless of where the air intake is located?

3) Is it okay to connect my condensate drain to a cheater vent (AAV) that's connected to a toilet in the basement? Example pic (not mine):

4) Would you recommend I get a Low Loss Header?

5) Is it required to remove the clay lining in the chimney before installing the new CPVC exhaust pipe?

If there's any tips you'd like to share about this boiler, please let me know!