I would recommend you ensure that the longest run is never more than 50% of the total weekly distance, and ideally closer to 33% if possible.
With that in mind, your long run is currently 8.2 miles = 13.1 km, run 3 is 3.1 m = 5 km, so you should make run 2 be around 5 miles at least.
In my training I try to keep the second longest (your run 2) around 2/3 of the longest. That rule of thumb also makes run 2 just over 5 miles.
The reason for the ratios is that this ensures there isn't too much of an increase for the long run, and psychologically you can always run the first 2/3 of it thinking to yourself "hey, this is no worse than I did earlier in the week, so the extra bit is really not that big a deal.
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