Road bike seat height?

I have the following bike setup:

Bianchi Limited 12 speed, circa 1990 ($35 at the Salvation Army)
Derailurs & Shifters - Shimano 105's
Brakes - "Dia Compe"
Seat - FEC Alloy SX (Very light but nice)
Gooseneck - SR Royal
Handlebars - SR Road Champion
Crank arms - SR 170mm
Front gear - Sugino 52-42
Rear gear - 25-23-20-17-15-13
Rims - Sun Mistral USA 700mm - 36 spoke alloy
Tires - Discovery Kevlar CyclePro 700x25
Tubes - Slime 700x self healing ($15 for 2 tubes)
Skewers - Suzue
Wheel hubs - Suzue 36 spoke
Valve stems - Presta (bought an adapter for $2)
Computer - Cateye Astrale CC-CD100 N ($25)
GPS - Garmin Etrex Vista ($339)
Communications - Yaesu VX-7Rb handheld ($319)

How do I adjust the seat height? I'm thinking the formula
would be frame size + crank arm + distance from top of
frame to top of seat should equal my inseam, right? Or not?
Measuring my inseam is with my feet flat on the ground - I
don't ride flat footed but with the base of my toes on the
pedals. Should I figgure this in?

Also, how do I measure the frame size? Is it from crank
centerline to top tube centerline (at the seat post)? I got
exactly 50cm this way

Frame size = 50cm?
Crank arm = 17cm
Seat height= 10.5cm
Total = 77.5 cm

I measure 29" from crotch to floor = 73.66cm. If I add
my feet that's another 3.25" or 8.255cm for a total of
81.915cm. By that measure I need to raise my seat 1.738"
or 4.415cm My seat is currently as far down as it can go.
I can just reach the street with both toes when sitting on
the seat but when riding, at the bottom of each stroke,
my legs are still bent and at the top of each stroke I feel
a bit cramped......help?

Ken