bottling day is the day when the wine is ready and in its perfect state to be bottled, not just a day when you have a day free to bottle.. you'll regret it later
If you need to bump up your must temps, use a submersible aquarium heater.. It's one of the most important tools imo, and its thermostat controlled..
I use the 300 watt
http://www.amazon.com/dp/B000YADYXG/?tag=skimlinks_replacement-20
Research Mycoderma.. it's most likely what you have… Get that barrel topped all the way up and wack it with a double dose of so2 according to your wine's pH.. wait a month and see where your at..
too much headspace and not maintaing proper level of so2 will cause mycoderma.. You need to immediately find a carboy that properly fits your wine's volume, top it all the way up, and whack it with double the sulfites according to your pH.. this needs to be done ASAP
3.3-3.4 is crazy low for Cab Franc, I'd finish fermentation, press, rack off gross lees after 48 hrs, then test pH again, and maybe bump it down to 3.7... I, personally wouldn't feel comfortable adding that much tartaric to go to 3.5
Alot of suggestions here.. All I can say is nothing works better than 300 watt submersible aquarium heaters.. your must will be at optimum temps within a couple hours
I use these all the time and they work like a charm, it heats your must up in a couple hours…
http://www.amazon.com/dp/B000YADYXG/?tag=skimlinks_replacement-20