Any jewish ancestor makes you a jew, it's just that the more non-jewish blood in a jew, the weaker he is(as a jew), but still a jew.
You are talking about a VERY distant ancestor, the information may be incorrect. Although no matter how distant your ancestors might be, the best way to find out if you are jewish or not is to do Satanic meditations and RTRs. If the meditations will bear fruit, and you will be able to perform RTRs without any special problems, then you are not a jew, since any jewish soul cannot do this due to its structure. Just keep in mind that it is possible to wage a spiritual war only after special preparations and putting up protection for the soul, and problems in meditation for a beginner can be caused not only by the fact that he may turn out to be a jew.
The more sermons you read and the more you understand, the better. A lack of certain knowledge can turn ordinary questions into paranoid ones.