A FAR of 1.0 means that that on the 87,120 f.sq. of one two acres parcel a 87,120 f.sq. sq ft building could be built or on all ten acres a 435,600 sq ft PROJECT of multiple buildings could be built.
If one PROJECT is built on the five adjacent parcels it could be built with four or less stories in height and utilize the allowed sq ft. and have one access to the adjacent streets
However because of the 100,000 sq ft per PROJECT limit a single multi-parcel project could not exceed 100,000 sq ft. so that approach would have to be discarded.
However, if five separate buildings of 87,120 sq ft each are built on the five separate parcels then, because of the separate parcel setbacks, each of those buildings would have to be five stories tall to use the allowable sq ft. and each would be required to have its own access to adjacent streets.
Moral of the story - zoning ordinances are complicated and trying to change one piece without carefully considering the impact of that change on ALL of the other pieces will produce some unexpected and undesirable consequences.