Evan Salant wrote

My question is this: What is the airspace below the floor of this
Class B airspace ? Is it Class G ?

YES

Would you be legal flying (daytime) simply "clear of clouds" ?

YES with 1 mile visibility

Could you fly with an 800 foot ceiling ?

YES, if you can comply with Section 91.119: Minimum safe altitudes

The regulations on this are a little murky...I've heard some people
say Class E goes all the way to the ground below B but could never
find this in the FARs/AIM.

It only goes to either 700' or 1200'. Ref: FAA ASF 92 / -002, "Airspace
Reclassification at a Glance".

Bob Moore