Galvanized pipe desk - measurements / layout? (Pic)

[Rex4748]

I'm planning to make a desk out of a butcher block and galvanized pipes, but I'm a little unsure of what the exact measurements / layout should be.
This is a rough drawing: https://i.imgur.com/3DkbhdS.jpg
Obviously the proportions of the drawing itself are way off, so ignore that and focus on the measurement markings.

Here's what I'll be using:
Butcher Block - Cut to 72"x30", 1-1/2" thick
Galvanized Pipe, 1-1/2" - Several, cut to size and threaded
Galvanized Tee, 1-1/2" - 8x, 3.6"x3.6"
Galvanized Floor Flange, 1-1/2" - 8x, 2.7"x2.7"

Here are my questions:

1. Is this an okay layout? Will the pipes support the weight of the block, which I'm assuming will be around 80-100lbs (plus the weight of my monitors, computer, etc.)?
2. Are 1-1/2" pipes the way to go? They're pretty expensive, but I figure they would help with stability.
3. Are the sizes on Home Depot's site accurate, as far as the flanges and tees go? They seem off.
4. How far in should the legs be attached?
5. What size screws should I be using to attach the flanges to the block?
6. What size should the pipes be? I could do some basic math to fill in the gaps, but it seems a bit more complicated than that. Because the pipes screw together, you'll obviously be losing a bit of length for each. How long are the threaded sections, and do they screw all the way in, or only partly? I'd like the desk to be as close to 30" in height as possible, but it's seems like it's going to be very difficult to be accurate with these.

Any and all help is appreciated!