I love your analysis! And you have prioritized your options - which is great. I think you are on the right track. Your plans seem sound. :) I don't see any roadblocks. And the front yard location will be stunning! I can't wait to see your planting plan.

Roof area and percolation test.... Roof area for front down spout is 795 square feet. Roof area for back down spout is also 795 square feet. I dug an 18” deep hole yesterday. I was dismayed to find extremely compacted sandy soil, virtually no top soil, little organic matter, not a worm in sight. It was like digging stone. The FIRST fill of water had not drained after 7.5 hours (still about three inches). It was empty this morning. Thinking maybe I was digging into the construction dirt from when the house was first built, I just dug a second hole further from the house. It’s the same dirt! Waiting for the first fill of water to drain right now.

Bought a house last year and unfortunately the basement flooded. We had a french drain installed in the perimeter of the basement and the sump pump is now temporarily draining to a trench alongside our house. Initially the plan was to connect the sump discharge to the storm sewer, but we are now exploring the possibility of a rain garden instead due to cost. Plus we like the idea of having a rain garden. We are thinking of putting it in our back yard and blending it in with current landscaping, keeping it 2' away from the fence. This is a point where the yard downslopes. Only downside is it is largely shaded. Also, on the other side of the chain link fence in our neighbor's yard there is an old dry well that has failed and this area gets flooded during heavy rains, requiring our neighbors to siphon this water to the street. The rest of the back yard would be challenging since there is a large maple tree and roots would be limiting, and much of the remaining yard would be uphill. The front yard may overflow onto the sidewalk, and especially since we don't know exactly how much water to anticipate with heavy rains, we thought that might not be a great idea. Since it was installed, our sump pump seems to be going off nearly every hour and it has been fairly dry. This especially makes us worried about possible overflow.

The photo labeled "two" with no snow... If you dig a gravel walkway from the driveway down to the rain garden location to force the water to the desired location the water will not affect the basement. Curve the walkway all the way up into the corner by the garage door, or use something very densely rooted as an edging to deflect the water to the walkway. Siberian or Japanese Iris work well for this,or even Liriope which is evergreen.