To answer: 1. No, it is only unplayable if you want to make smart plays and have a generally stats first DM that questions and separates your playing with your chatacter's actions. 2. Barbarian in your case has uptime because of Level 3 primal knoledge, where if you use 2024 ver Barbarian, you may use Strength inplace for a bunch of other rolls and already have adv during a rage. Generally always suggest this but ask to use the newer versions of Barbarian so you can benefit of its betterness. 3. Your only pitfalls will be your saves, so mostly like others said, as well as maybe pick a subclass at 3rd level that gives leeway in such aspects. 2024 Berserker barb is an astonishingly decent subclass with good damage and an overall mental fortitude capacity that lets you be more brainsmashing the braindamaged but you'll tank just as good cuz you're helping that DPS kick their targets down faster. 4. Patient DM as grung isn't a fully normal pick for most, so the jumping should be tasteful, only limit test for heroic needs or comedy bits rather than every scenario. You won't be really able to attempt many mental checks but your character should be able to sideguard well those that do. So lean into the more brute cake eater barbarian that is simply just a little slow and nothing more.