Can someone tell me is it OK to use red wine for cooking which has been opened for 6 - 8 weeks, it has been kept at a low temperature.

Depends on what you mean by OK.
After this amount of time, even cooled, it will of started to oxidise and loose all of it's fruit and balance.

Honestly, bin it.

I wouldn't use red wine that's more than a week open, even it's it's been vacuumed. It goes off.