5.3 is a normal mash pH. Maybe a tenth or two lower than you'd want for most beers.
So next time you're brewing something fairly dark (5% Carafa is quite a bit), you could add a little alkalinity to the mash, or just not add the calcium salts, or not dilute, and you should be able to bump it up a bit.
I don't think you're doing your RA calculation correctly:
RA = TA - 0.71[Ca] - 0.59[Mg] = [HCO3]/1.22 - 0.71[Ca] - 0.59[Mg]
I get 156 (as ppm CaCO3) for the base water and 80 for the mash water as posted.
Edit: FWIW, I downloaded the EZ spreadsheet and it does calculate the RA correctly, so you may have an input error somewhere.