how much can I expect in actual cat if my scores are around 50 in cracku mocks?

ditto

80 percent

No clear answer. The Cracku mocks are definitely harder but on the day of exam you may be under additional pressure. Hence there can be multiple factors effecting your performance. There's no point in analysing this question. Keep practicing and don't give up! Best of luck :)

Maintain your calm on the CAT day i have heard students do miracles and miracles are not always jolly they are disheartening too some either get what they want others lack composure and panic at times on the d-day nothing is evident keep grinding and stay calm on the d day rest even 90 percentile is not a big thing 20/20/20 is 90 percentile these days.