Can amyloidosis cause a hypoplastic bone marrow?

No: I would look for a different cause. Some amyloidosis (famously amyloidosis al, made from light chains) is caused by a subtle or not-so-subtle proliferation of plasma cells; this may be treated with marrow suppressors. In an older person, "hypoplastic marrow" may be from sampling a place where marrow was a bit scant; the blood picture's key here. Your physicians know more. Good luck.