Homebrew Feat: “Whirlwind Sentinel” –critiques and suggestions please

The DM and I have worked it out, so it’s a bit moot, but I’d still like the community’s opinion on whether or not this homebrew feat is balanced for D&D 5e.
Inspiration taken from:
Sentinel (PHB 169)
Slasher (TCE 81)
(Sorry, feats not in the SRD)

This is for my lvl4 halfling barbarian; he has a STR of 17, so I really really want that sweet +4 mod, but taking the attr bonus is ‘boring’ to me. The purpose of this feat is to give him some more battlefield control (a la Sentinel; plus he took the Wolf Totem option at lvl 3), while also limiting the instances he can ‘do the thing’ (a la ‘Slasher’ feat)
Here’s what we came up with:

  • Increase your Strength or Dexterity by 1, to a maximum of 20

When using ONLY a melee slashing weapon* (with or without a shield):

  • When you use your Reaction to hit a creature with an Opportunity attack: if you don’t have disadvantage, roll a second d20– if the second d20 would also hit, reduce the creature’s speed to 0 for the rest of the turn.
  • If a creature you attacked on your most recent turn makes an attack against a target other than you, you may use your Reaction to make an attack against that creature

*we wanted to underline that this feat only works with slashing weapons, but not prevent a flaming axe or shields