بسم الله الرحمن الرحيم
(1) Yes, Al-Yasa is good name as it was the name of a prophet thus you may give your child this name Muhammad Al-Yasa.
(2) For the spelling of Muhammad Al-Yasa contact some Alim who is expert in English and Arabic languages. I am not aware of the complicacy of English language.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.