Note: I had an unintended direct conflict in step 4. tx_HS needs to be evicted indirectly as a child of tx_LL. As I described it above, tx_LM would be a direct conflict with tx_HS and therefore would need to beat the individual feerate of tx_HS. It can be easily fixed by introducing a third confirmed input c3 that is spent in addition by tx_RBFr and by tx_LM instead of c2.
I‘ve updated the charts here: https://bitcoin.stackexchange.com/a/121542/5406