I think it’s more useful to look at average daily lead intake and compare to that baseline instead of arbitrary limits especially as you’ve noted there is no way to set a “safe” level of lead exposure

for adults this comes out to about 0.3μg of kg body weight - so at 70kg that’s 21μg of lead which means that adding an extra 7μg per day via that huel protein increases your lead intake by a third - so it’s up to you to decide if you think eating 30% more lead just for the gainz is worth it - i personally don’t