One of my side line activities is wood/shop dust management/consultant so in the course of this I visit a lot of shops - both pro and DIY shops, and provide advice on this matter, and BSM Dust management inside a building can be tricky.
The logs are usually loaded on the side opposite where the sawdust is ejected and as the loading side needs to be near an open side of the building that places the sawdust production on teh other side of the mill so closer to the middle of the building. I see you are using what looks like a snow shovel? to handle it.
I agree about having to wear a respirator all the time when milling is a right PITA. I so have a full face respirator which runs off a battery pack attached to a waist belt but I find it very claustrophobic and at times they don't put out enough air especially when its hot.
As far a fans go you might want to take a look at barn ventilation fans.
The one in the photo below is a 3HP unit that runs straight of (ours is 240V) regular mains power and is being used at a large country "Mens shed" (community shop).
I personally don't like these fans as they are noisy but they sure do move heck of a lot of air.
Where I live it rarely goes below freezing in winter (maybe a few hours in the whole year) and although it can get very hot in summer most of the rain (~28" a year) falls in short heavy falls during June-Aust so I still opted to set up the BSM to use its outside. It's also relatively windy most of the time so there is always a breeze blowing the dust away.
Theres also lots of room around the mill to used a forklift and a loader with a bucket to scrape up the sawdust.
I realise this doesn't suit many folks especially in climates where the weather can be quite different.