Going by that promise, Pence is running to handle "domestic and foreign policy."
"Domestic" and "Foreign" Policy are literally the only types of policies there are, so this definitely isn't accurate (Unless you're trying to say that pence actually would be handling literally everything).
At the very least, he'd be one heartbeat away from the Presidency
Not exactly a "heartbeat" away. Out of all 44 us presidents, only 8 have died/been killed in office, and one has resigned, bringing it up to a total of around 18% of presidents who have been replaced by vice presidents.
Given that trump has a 38.4% chance of winning the presidency as of now (http://projects.fivethirtyeight.com/2016-election-forecast/#plus
), That puts pence right at a 6.9% chance of becoming president. Again this isn't anything close to a "heartbeat", and it's certainly far less than Hillary's 61.6% chance.
and in charge of the Senate.
It's inaccurate to say that the Vice president is "In charge" of the senate, since it implies that he actually has some control over what happens. His job is pretty much to sit around and watch, and the only time he has control is in the event of a tied vote (which basically never happens).
Don't think that excuses him from criticism here.
I never said it excused him from criticism, just that it doesn't really matter if he makes mistakes.
It's sort of like the difference between making the mistake of pissing your pants in the senate building (Which is pretty much the extent of the vice presidents powers) And making the mistake of signing an executive that says to nuke russia.