What is an acceptable risk of ruin?

Under 1% across the trades you expect to take in a year. Above 5% means the strategy is likely to end the account before its edge is realised.

Does a high win rate protect against ruin?

Much less than traders expect. Risk per trade dominates the calculation by orders of magnitude.

0.25% to 0.5% for most retail accounts, because gold can travel $25 to $40 in a New York session.

Yes, which is its main limitation. Real losses cluster by regime, so the true probability is higher than modelled.

Risk of ruin is the probability a losing sequence takes the account past a threshold before positive expectancy can show.

Risk per trade dominates the answer: the same edge is safe at 0.5% and reckless at 3%.