You live in Michigan (I spent my formative years there). You have two seasons. Winter, and the other couple of months (which also coincides with Pothole Season).
You absolutely need a fully functional flapper valve. Without it, liquid fuel will fall out of suspension from the air/fuel mixture, collecting in the bottom of the cold intake runner, then pouring into the combustion chamber where it will fail to burn and thus slip past the rings, wash off the oil film on the cylinders and end up contaminating the oil in the crankcase. Gas contamination in the crankcase will wear out bearings and every other moving part prematurely.
These flapper valves had side clearance allowing for to-and-fro movement of the shaft. Light hammer blows to the weight and and the other end of the shaft may aid it breaking to bond between the shaft and the manifold.
I recommend that you begin the process over again with heat, Kroil, and LIGHT hammer blows to the shaft ends. Once you get even the slightest lateral movement of the shaft from the hammer. Kroil will seep right in there. Don't count on noticing that movement, just heat, hammer, and apply Kroil several times over a number of days. It will free up.
