If the government does shut down on Dec 21, could this delay if not halt newly won government contracts with private contract holders?

Funds are obligated at time of award so they cannot be pulled for any reason other than a termination or reduction of scope. If it is incrementally funded, then there maybe some impacts since a funding mod couldn't be executed (unless using no year money). Very few contracts are funded like that so I don't think you have anything to worry about.

It is possible. That being said, if the money that was paying for these contracts has already been set aside out of a previous budget it should not affect it at all. The government shut down affects future expenditures. For example, if the previous budget was used to pay for a contract it will continue as planned. If a contract was agreed on but it was set to begin from a new budget (e.g. the budget that is being delayed) it will not be paid for just yet.

Upon further review I think I am in the clear as far as funding goes. The funds used to make this position available came from USSOCOM under the POTFF and awarded to Nobilis SRS in June this summer. That being said it is from previously budgeted funds and 'should' cover the 5 year term of this contract position. My concern now however is whether or not a shutdown would delay my mission visa approval time. It is routed through Germany, then Rome, then US Italian consulate where I then go to pick it up after making an appointment to go in and collect it. Being those are all outside the US Government I think I'll be in the clear.