Where did you find the specific (link) information that BFD is supported with VRRP?
The lowest you can get with VRRP is to use fast interval which allows minumum 100 milliseconds
set vrrp-group "#" fast-interval 100
These are the protocols supported by BFD on Junipers platforsms(that I amcurrently aware of): OSPF, IS-IS, RIP, BGP, PIM, RSVP and static routes,