Your model continues to boggle my mind.
I try to perform at least one Bitcoin transaction daily. Either by spending some, buying some, transferring some, or most often by receipt of mining earnings.
Suppose that I am responsible for permanently increasing the daily quantity of transactions by one. Today's adjusted number of transactions reported by Blockchain.info is 58,006, and your model projects a market cap of $1.50 * 58,006 * 58,006 = $5,047,044,054.00. My contribution makes the adjusted number of transactions 58,007, and the corresponding market cap is 5,047,218,073.50. The difference between the two market caps is $174,019.50. As the total number of Bitcoins at the time of writing is 12,591,775, my one incremental daily transaction lifts the corresponding price per bitcoin by 0.013 USD.
And this is why Quantity Theory of Money says M x V = value, not M alone. This is why selling out to fiat via Bitpay robs us of the square of the count of transactions and puts that value in fiat instead. The value of a network is the velocity times the position, not just the position, i.e. if all the actors (hodlers of money or nodes) don't interact then the network is a beautiful pile of do-nothing.
Using bitpay keeps BTC in the air. That creates a churning marginal demand which decreases the supply on the fiat market. If you buy immediately before spending, and the merchant takes fiat, then the time in the air is small. If you buy in anticipation, V decreases, and the effective air time, from the point of view of the exchange market, is quite long. Using bitpay also adds to the bid and to the ask on the market, thus increasing liquidity, which in turn makes bitcoin marginally more efficient (less slippage) and less risky (as liquidity is available when it is needed).