Service from GTA to GTA

Hi

We have a business having 200 crores turnover of goods and we used transportation service from various transporters. To increase profitability we decided to buy our own trucks for transportation. In return we will give a contract to some transporter "X" for transportation from the city of our customers to our own city. We will take GTA registration and raise the bill on the transporter "X" for approx. 90% of the actual transportation. We face the following issues ?

1. Whether we have to charge GST on the transporter "X" or not.
2. Whether we have to add GTA Service in our GST Registration. Which option should we opt for. Forward or RCM. 5% or 12%.
3. Whether any dispute on existing any type of tax raised on the whole turnover including existing 200 crores.
4. Whether we have to issue any consignment note.
5. Last and most critical, we have a mix supply of taxable and exempt supply. We avail credit of input GST in ratio of turnover of taxable goods to total turnover. No input will be used for transportation service turnover except the purchase bill of the trucks. If we opt for forward charge then how much cenvat of trucks can we avail and how the effect of the part of transportation sales service into total turnover on input of other goods and services.

Please give advice.

Thanks in advance.