If you are referring to the Fed repo market operations, then these are short-term collateralised loans, so not really the same thing as pumping trillions in to the real economy.
A fiscal stimulus of that size would almost certainly drive demand (during a pandemic that has caused a negative supply shock) and therefore increase inflation.
At a minimum doesn't the CARES act transfer at least $500 billion to SMBs and unemployed people, via PPP and Federal supplemental UI? And since this is all deficit spending, it's implicitly backed up by the Fed being willing to purchase Treasury issuances? My point being that if you buy into MMT and you don't think what has happened in the last couple months has created any inflationary pressure then you probably believe you can spend another trillion with little risk.
I'm not sure why you'd need additional taxes at all, when it seems that deflationary pressure is so great that you can summon up trillions with little inflationary consequence. $35 billion/year seems like nothing compared to this.