85.8 grams of DNA is enough to overflow 64bits. Not that we're anywhere close to being able to use or process information on those scales, but it at least storage on that scale doesn't outright violate the laws of physics/information theory.
That said, how to you make your calculation about DNA's information density? Without counting water, I've arrived at 720g for one “mole of bits”, which is a bunch of orders of magnitude higher than your figure: 2 amino-acids (262g/mole) [1], 2 Deoxyribose (135g/mole each) and 2 Phosphate (94g/mole each).
[1]: and it's the same value be it A-T or G-C, that's interesting
[1] https://www.scientificamerican.com/article/dna-the-ultimate-...
I do not know why Laremere chose 85.8 grams though as these are quite above the 64 bit limit, unless I got my multiplications wrong :P
"The male nuclear diploid genome extends for 6.27 Gigabase pairs (Gbp), is 205.00 cm (cm) long and weighs 6.41 picograms (pg)."
Or, many many orders of magnitude less than 85 grams...