Be extremely careful when using 'vanilla extract' you get in the store. Very often it's made with the cheapest vanilla beans they can find. Just as often it's vanillin extract, which is NOT vanilla extract.
I would use high quality vanilla beans in anything I make/brew. You can get them for short money on Amazon (bought my first 7 beans for under $7 total). Don't use the prices they charge at the grocery store as any guide (you're probably getting graped there).
Another option is to use some oak chips and then age it for a few months. After that amount of time, any oak flavors will have mutated to vanilla. I had this happen in a brew I made, with the chips. Same thing won't happen when you use cubes, staves or spirals. Go figure.
I would plan on leaving it in primary until it's actually READY to go to the next step. Thinking that it will be there after 2-3 weeks is wishful thinking (at best). While it MIGHT be 'done' fermenting by then, chances are it's no where near ready. You CAN (and many people do) age on the other elements in primary if you want. If you're not 100% positive of your racking ability (being above board) then leave it in primary until it's time to bottle/keg it.
Also, be aware that you'll need to taste the batch periodically. So, get really good at doing that safely. Easiest way will be to use a beer thief, or long turkey baster, along with a couple of paper towels, or clean cloths, soaked in Star San. Put the airlock/stopper on one of them, extract the sample, then cover the fermenter opening (assuming carboy or other small opening item) while putting sample into something. Then spray the stopper with Star San and insert it back into the fermenter.
BTW, IMO/IME, an OG of 1.070 isn't all that big. Especially for a 'winter warmer'. Also, IMO, anything under 8.5-9% really won't qualify as a "winter warmer". Sort of like how some places have produced barley wines (or call them that) that are under 6% ABV.
