The RO90 really is a bit too small for this kind of job. Looking at the pics I suspect the paint is really old lead paint and some of that stuff is incredibly hard, especially if it's a thicker layer. I think a chemical stripper would get the quickest result and keep the contamination as low as possible.
A heat gun can work but it is also pretty slow. I once made the mistake of buying a cheap gun for about that price, and threw it away after 20 minutes as it did absolutely nothing. The professional gun I got now at least works as advertised, but is still pretty slow. Using a torch is definitely the fastest solution, but unfortunately not for indoors.
Ye I the ro90 is small I tried to get the 150 but by the time I bought the sand paper and the ro150 it was to expensive at the moment you can get shapir in p24 in 150 but not in the 90. That's my fear is the smell in the house with the heat gun or chemicals thanks for the help
