Double floor joist for the stairwell is load bearing, to a point. It is self supporting for the well/floor and light partition walls around/above it. Not if there is a middle of the house wall that supports the ceiling/floor joists of the space above (living space attic or second floor or roof rafters braced to it). If your house is average design, your metal i beam should be that. I think your plan works except the hole drilled through it for pvc pipe and maybe you can reinforce the spot with metal bracing. It is close to the foundation, but i don't know the rules for the load bearing beams.
I'm sure it is sold in singles.
S33021 - Jones Stephens S33021 - Single Stud Shoe, 18 Gauge, Box of 50 (Galvanized)
Jones Stephens S33021 - Single Stud Shoe, 18 Gauge, Box of 50 (Galvanized) - Jones Stephens S33 series single stud shoe with 18 ga thickness has 4 nail holes on each side to provide convenience usage to the user. Stud shoe has galvanized finish that provides protection against corrosion and...