Banks' private-credit lending constitutes part of their risk-weighted assets. So yes, it's part of their CET1 [1], which is part of Tier 1 capital, and since it's equity measured it incorporates fucking everything.
4.5% is the U.S. minimum. Regulators start throwing their toys out of the pram when a bank breaches 7%. To be clear, I'm not seeing anyone in the near future breaching those limits. Deutsche Bank, the stupidest of the lot, seems to have let DB USA stuff most of the risk in its German AG.
[1] https://www.investopedia.com/terms/c/common-equity-tier-1-ce...