OK, so your issue is the feat is poorly designed (and a bit redundant - why do I need to restrain when the feat already gives advantage). That is a different issue. I think a feat seems appropriate, but I could also see it as part of a fighting style. My only point being I think the idea that it is not free makes sense.For reference:
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1. Its a feat. Although most games use feats, not all do. I agree being able to restrain should require some training, but a feat? shrug You are already using a second attack to progress from grappled to restrained, that should be sufficient. Now, if you grapple and attempt to restrain, but fail, then perhaps the creature escapes automatically or at the very least allow advantage on the next escape attempt.
2. If you restrain a creature, you are also restrained. Which means your speed is also 0, so you can't move the creature. Your speed should not be reduced as it is already half when attempting to move grappled creatures.
3. The Restrained Condition is weak. A restrained creature should not be able to take any actions other than trying to escape being restrained. What is Restrained should be more of a Grappled Condition (at least the new playtest material is heading in the correct direction in that respect...), but with half speed instead of 0 speed.
4. It deals no damage. If you want to deal damage, you also need to take the Fighting Style... The feat should make your grapple deal 1d4+STR mod damage IMO.
However, didn't you already break everything down to half feats?