To combat fog, you need to pull it, which would require overexposing it before underdeveloping it, which would mean using an ISO lower than 6, and a time less than 4.5 minutes (if those are in fact known to be reliable values for the film originally.) But hey, you only have the one roll so it's not like you need to scientifically hone in on the optimum specs for it. Maybe just try shooting it at ISO 6 and developing for 4.5 minutes and see what you get!
Is that ISO of 6 taking into account the IR filter? I often see IR films stated that way - it's really ISO 100 but when using the filter you need to adjust by a bunch of stops so when using an external meter or an internal meter that doesn't "see" IR, you need to use a much lower ISO value. In any event, like any IR film, you'd be well served to bracket the heck out of any shots you make!
Duncan