I would consider a hood.
I thought he had a hood but no- right? And maybe that will help direct the hot air, steam and fumes towards the vent.
There definitely is an issue if you are not getting 100% blue flames. Might be a problem of too
much gas. What size are the lines? This may be one of those multiple issues type of a problem with no single solution.
My hood only covers about 1/3 of the kettle at most but there's only about 3" above the the top. It pulls very well- especially if I crack the lid in that direction. An I like to crack the window opposite about an inch. That helps a great deal.