Yes, but almost all use fractional Kelly (half or quarter Kelly), not full Kelly. Full Kelly is too aggressive for real-world sports betting where edge estimates are imperfect.
At -110 odds (standard), you need to hit 52.4% to break even. If you're hitting 54-55% and using Kelly correctly, you'll be profitable long-term. If you're under 52%, Kelly will correctly tell you not to bet.
Weekly minimum. Your bet size is a percentage of your current bankroll, so if your bankroll changes by 20%, your bet sizes must change by 20% too.
Yes, but your bets will be small. A 3% Kelly bet on $500 is $15. If that feels too small to be worth it, you either need a bigger bankroll or you need to accept that slow growth is how this works.
Overestimating their win probability. If you think you've got a 58% edge when your real edge is 53%, you're betting almost twice as much as you should. This is the fast track to going broke.
Only with reduced fractions (quarter Kelly or less). Live betting has more uncertainty and less time to analyze, so protect yourself with smaller bet sizes even when you think you have an edge.
Only if you have reliable data and a proven edge. Most recreational bettors don't. Player props are often priced with heavy juice, so your edge needs to be significant to overcome the vig.
Kelly prevents ruin if your edge estimates are accurate and you use it correctly. But if you're consistently overestimating your edge or betting on games where you have no edge, no bankroll management system will save you.
Then either your bankroll is too small, you're overestimating your edge, or you should use a more conservative Kelly fraction. Never bet an amount that makes you uncomfortable regardless of what the formula says.