HI and welcome to the board. Are you planning on putting weights into the quilt to get it to weigh this much? Like the weighted blankets they make for people with Autism? Here is a blog that should help you. But that 35lb sounds to heavy based on this link which states 5 to 10% of the adult's ideal weight. At the high end you are making something for someone whose ideal weight is 350lbs?? Maybe you want to double check that. I will let other posters answer you question about batting as I have never made one and the tutorial I linked to doesn't mention using batting either. But someone who has actually made one may know better.
https://www.mamasmiles.com/sewing-tu...nsory-blanket/