Sessions needs to un-recuse himself and reassume control of the department that he was confirmed to oversee.
To be cleared of obstruction of justice, one has to be investigated for obstruction of justice. The more Bolshie donors in the investigation, the less likely a not true bill is not accepted. However, a contrary verdict would be subject to the recusal of Mueller.
I see the regulations, but I don’t think that it really serves anyone to force out Mueller.
Better to appoint a special prosecutor to look at Mueller and whatever papers he sign to take the job, call Comey to testify about his relationship with Mueller. If it can be shown that Mueller perjured himself or somehow obstructed justice by taking a position he knew or should have know he didn’t qualify for, try him for a felony and look to lift his government pension.
In fact, if Mueller were to submit a letter of resignation at this point, after he stirred the pot so much and hired so many questionable individuals, President Trump should refuse it and insist he stay on.