robus
Lowcountry Low Roller
I think it would be fine, however I would take a level of exhaustion for each use of the ability. Which yes, it means Disadvantage on Ability Checks for the first use of something which right now doesn't come with any drawback. But looking at the Exhaustion levels, most players won't care much until they hit Exhaustion Level 3 (level 2 is speed is halved). Make every use of the ability a physically exhausting effort which leaves you feeling it's use afterwards. If you want to use it 5 times in a day and risk death, go for it.
Absolutely - every time you push past your limits you gain another level of exhaustion.