Hi Nandu,
1. With the current implementation and design we have, it is not possible to have the custom terms in the "Contract Item Information" tab. But in 15s we are building the meta data structure for the line items in contracts (Contract Line Items Document). This is going to be very similar to what you have in Sourcing. So the vendors can see and respond to those custom terms directly. But the export of this Line Item Document is also in the same format as earlier. Please raise an ER on this so we can have a look at it and see whether it will be useful to have all this info in one single tab.
2. I do not know of any workarounds at this point.
Hari