Interference at 2nd? 1 out or 2?

[jTheUmp]

Hopefully I can describe this correctly:

R1, 1 out.
Batter hits a roller to F6, who fields cleanly and throws to F4 for the force out at 2nd.

R1 (now a retired runner) does a 'pop-up' slide, and F4's throw to F3 hits R1's helmet. R1 never actually made contact with F4.

Interference?

Defensive coach wanted interference on R1, and for me to call BR out as well.

My ruling was "intereference on R1, which did not prevent a possible double play (9th grade game, most infielders aren't quick enough to turn a 6-4-3 double play at this level, and BR was a fast runner). R1 is out, BR gets 1st base, play on." The next batter struck out, so it didn't make much difference either way.

But now I'm wondering...

Looking at 8-4-2b Penalty, I think maybe I should've called BR out in addition to R1.

But to me, the slide didn't appear to be illegal (it didn't fit 2-32-2a because R1 never made contact with F4... but I wonder if I could've used 2-32-2c instead).

I realize this is probably a HTBT situation... did I kick it?