What everybody else said. You are over-thinking this. Our college educations do this to us. The DCS "specs" are for the least powerful rangehood that DCS recommend for use with that stove, as akchicago says. As Weissman and akchicago (and now me, too) say, it is not the number of burners you have going but what you are cooking that determines the rangehood setting. You run the hood at the speed that is needed for what you are cooking regardless of how many burners you are using at the time. If you are holding various kinds of melted chocolate in six 5" sauce pans with all six burners going at once --- and I've seen my neighbor do this with four burners when making the most outrageous chocolate truffles you can imagine --- there will be no need to even turn on the hood. Yeah, you would have all six burners going, but there will be neither much heat nor any vapors to dissipate. OTOH, if you are into gonzo searing where you have one single pan heated hot enough to melt lead . . . well, you will probably need to open windows, use a floor fan and run your rangehood on high even though there is only one burner going. So, we have a unanimous vote here that you are okay running the vent at whatever speed works best for what you are cooking. Feeling reassured?

MUA systems can become quite elaborate, but it may be best to start with simple DUI approaches to see if they work well enough. You want the house pressure to not fall much or the fireplace will at best not draw properly. Fireplaces only draw as it is because there is normally a slight differential pressure between the hearth and the chimney exit. Say that you have a true 600 cfm going out, and some house leakage that we will assume is unknown. Then you need up to 600 cfm of make up air; more if there are also bathroom fans in use, or a dryer, water heater, furnace, etc. You could adapt the air conditioning intake ducting to pull in outside air when the pressure became negative. The issue is how much air will be pulled in through that path versus the house pressure. If it isn't enough (the pressure is still too low), then some additional flow is needed. This could be done by blowing outside air into the air conditioning ducts. This may work in very temperate areas where heating is not needed. A less lossy path might be considered where outside air is pulled in through a damper. Again, cold air may be a problem. A blower may be needed. Unlike commercial hood and MUA setups where the ventilation is usually run at a single speed and hence the MUA can be run at a single speed, the residential hood blower is usually variable. Balancing the system for various conditions, including open windows or not, bathroom exhaust fans on or off, etc., can be a challenge -- one I am still working on for my own system. Another stage of complexity is to heat the incoming air. This means another furnace circuit, or an electric heater and some large conductors. And all of this requires more ducting, a suitable intake assembly on the roof or exterior wall, controls, etc. Sometimes the physical configuration of the house makes such a system impractical (giving the benefit of the doubt that any MUA system is practical). You may wish to plan on open windows in a remote room that has a very good heating system to temper the air. A kitchen window can work, but tends to disturb the rising effluent of the cooking process, causing some to miss the hood. kas

maybe disconnected? anything bumping around under the house in the past few days or nights? I'd take the supply grill off and look inside with a flashlight. see if you can see inside the duct. best of luck.

It could be refrigerant leaking, but I doubt it personally. R410a refrigerant has a sweeter odor to it. It could also be dirty sock syndrome. Search that on Google and you can learn about it. A service tech would be able to properly diagnose this issue and propose a solution. Take care.