Most cabinets these days have a thin veneer over particle board.

smell is different than smoke particles.

However, on the inside of our house it was far exceeding the normal ranges (normal was something like 700 particles per square meter and we had something like 1777 particles per square meter).

I already went through this in my former career with the diesel engines on our excavators: at EPA Tier IV Final the particle count allowed in the exhaust was less then the average ambient air in a city - which effectivley turned the diesel engine into an air clearner.. 

Vacuum carpets and upholstery to remove loose particles.

It's one of those, "if all the stars, planets, AND moon particles align" type scenarios which is unlikely at best. 

Water in the seam or anywhere it can reach the particle board substrate would be the only problem.

Particle board on the bathroom floor is never a good idea. 

My units were pretty cheaply constructed and have particle board subfloor (underlayment, really). 

That era of MH's used formaldihyde in the flooding if it was particle board which most floors were in those days.