Collecting interest on proceeds...

While the intermediary holds the money, can I withdrawal the interest monthly?

The answer is NO. Section 1031 will not allow you to touch the money in between the sale of your old property and the purchase of your new, not even the interest. At the end of the exchange, you may have the interest sent to you in a separate check, or you may include it in proceeds that the intermediary transfers to the purchase of the new property. And yes, it is taxable to you, no matter how it comes to you.