What are the chances of getting at IIM ABC, FMS, or XLRI if 10/12/grads' percentages are 65/82/65?

More than the 10th, 12th, and graduation percentile, it is the entrance exam marks that matter. Getting admission in IIM ABC, FMS, XLRI is also not impossible if you somehow manage to score well in the CAT.

There is a selection criterion for every institute. For example, an institute like IIM C has a merit-based selection system in which they prefer students with higher percentile. IIM B focuses more on the distinctive profile and a little less on the percentile. FMS has reserved its 60% criterion for the CAT marks. In this way, every institute has its own criterion for selection. It will be tough to get admission at IIM A as it demands a high cutoff for graduation as well.

So, apart from one, all the other options are open if you can secure a good score in CAT.