If it is not possible, is there a way to know the count of outliers for each timepoint, and the value of 'median + 3.5*MAD'?

Sure, "3dToutcount -range fred+orig | head".

That will show you the top 10 lines of output. But the
"3dToutcount -range fred+orig" command gives you exactly
the information that you are asking for, if you do not
plot it with 1dplot.

If you just want to note which TRs have the outlier count
exceeding the MAD line, then you could use 'awk':

3dToutcount -range fred+orig | awk '{if ( $1 > $2 ) print NR-1, $1}'

Note that this is going to give you lots of numbers, and
you may not care about any of them, even if they are large.
Your best guide to search for problems is to use your eyes,
scanning the time-series with afni.

- rick