I just now noticed you've made a small error, you wrongly copied the helium density from Wikipedia, it should be 0,1786 g/L. This brings us closer to hgordon's approximation seeing as a difference of 1 g/L = 1 g/dm³ = 1000 g/m^3 = 1 kg/m³.

If you do the math now, you'll have more than double the lift you had previously calculated.

Thank you hgordon for that approximation, otherwise I wouldn't have noticed the density used for helium was wrong.