“1. He claims he will do things like abolish the IRS, which the president has no authority to do. This is a constitutionalist?”
What branch of government does the IRS belong to?
The IRS is an agency of the executive branch.
However, I do not believe the president has authority to abolish agencies established by law on his sole authority.
The Constitution gives the taxing power to Congress, with all laws affecting taxation originating in the House. Congress created the IRS to implement the tax system it established by law.
If the president can just ignore these laws when he sees fit, then the power to tax (or not tax, the same thing) has been removed from Congress and appropriated by the President.