Ok, We will go one by one.
1. Applicability of Tax Audit does not depend upon profit margin of the business. If the assessee is required to get his Books of accounts audited under the Income Tax Act, then it is irrelevant to determine whether he has a sufficient profit margin or not.
2. If his commission income is more than one crore, then he compulsorily required to get his books of accounts audited.
3. There is a provision under which assessee can declare his income on a presumptive basis but only when his turnover is limited up to 2 crores and also he is not required to get his books of accounts audited. BUT THE IMPORTANT POINT IS, ASSESSEE EARNING INCOME IN THE NATURE OF COMMISSION CAN NOT DECLARE INCOME ON PRESUMPTIVE BASIS. SO THIS SECTION IS IRRELEVANT FOR YOU.
4. With the Finance Act 2020, Audit of Tax audit limit is relaxed from 1 crore to 5 crores if the assessee fulfills the following two conditions (a) Cash Receipts (includes all types of received in business) does not exceed 5% of Gross Receipt. (b) Cash Payment ((includes all types of payments in business) does not exceed 5% of Gross Payment. REMEMBER PROVISION STATED IN POINT NO. 4 IS APPLICABLE FROM F.Y. 2020-21.