Oh c'mon folks. This is interesting to me. Something's going on here.

OP, I'm curious about how you got this bike. It's obviously an older bike and you're a big guy. It's not easy to find a just-right used bike. Or have you had this bike since you were a kid? Anyway, the fit you've come up with might very well be the best that can be done on that bike. I'm curious to know if this is the case, so . . .

Try this:
Go to an online bike fit website, this one: https://www.competitivecyclist.com/S...ulatorBike.jsp
Specify that you want a road bike fit in inches.
Put in all your dimensions. You may need to have someone help you get the measurements. Choose the competitive fit.

You'll get a long series of measurement for your prospective bike. You're really only interested in top tube length, which is really effective top tube length as many bikes now have sloping top tubes.. Everything else can be modified.

Compare that top tube length result to the length of the top tube on the bike you have. That length is measured along the center of the top tube, between the centers of the seat tube and head tube.
How does it compare? Report back.