I don’t think he served enough time in the Senate to earn that pension. I believe the minimum is 5 years.
Pension or not, if he is not a US citizen of any sort (NBC or otherwise)when he served in the senate, he would have to forfeit the entire senate salary he fraudulently received plus all of the presidential stuff. Hey maybe we could send him and his wife the bill that they ran up for all of their vacations on the federal dime.