Yes you do need more CFM's for exhausting fumes, and I had to put ear plugs in to watch your welding video, ha.
KC
My neighbor gave me a 24X24 inch squirrel cage blower, with a 1/2 horsepower belt drive motor,,
I have it mounted up high, and it is aimed at the main drive-through garage door.
I plug it in when I am gonna weld, it LITERALLY sucks EVERY fume out of the shop.
AND, since it is no where near the weld, there is no draft to bother the weld quality.
I also have a 48" roll around, belt drive, fan, but, that thing is so big, it causes drafts,,
With the squirrel cage blower, you never even smell a weld fume, unless you stick your head right down into the weld area,,
My wife used to complain about my clothes smelling like weld fumes, after a project,,
No more, if the fumes are gone, they can not smell up your clothes,,,:thumbsup: