The correct term is terrorism: the unlawful use of violence and intimidation in the pursuit of political aims. And indeed, this is the term used by police and the FBI director, see https://www.youtube.com/watch?v=HAfaa0AWVPw and https://www.youtube.com/watch?v=Da7HR3vnpGc.
Power in a Parliament is not proportional to number of seats.
As a simple example, if a party controls 51% of the seats, it has 100% of the power.
So you have finely tuned the number of votes that each party has, but you have not had a proportional effect on the power or influence of that party.
The greater difficulties (Hey Joe, you are on 0.05 of a vote, ...
You could not have secret ballots any more. The holders of fractional votes would automatically disclose how they voted. Secret ballots do happen in some parliaments, at least on some issues.
You could get/encourage a large number of partial legislators. They each need a chair, a desk, an office. How large does the building need to be this term, how large ...