You’re correct. That will be the straw that breaks Hillary the camel’s back. The leaks have indicated it’s a two pronged investigation. The money laundering and tax evasion are massive. The criminal mishandling of classified information seems to be confusing people.
The general public will understand her criminality associated with tax evasion. Even Obama won’t be able to find a rug big enough to sweep that under.
The private server and the chicanery around the Clinton Foundation are both (legally) very serious matters. However, you've nailed why the Foundation may be what ends up making it impossible for the Dems to back HRC: people understand old-fashioned bribery. Toss in some class warfare when more info about the staggering sums the Foundation has taken in gets out, and HRC will be toast with the general public.