Honestly, I feel like the candles are a greater hazard than they are a safety. Fire=Bad. Keep the room ventilated. Just to give you an idea of some approximations I just made.. Bear with me, it is early in the morning so I can not show all my work because I have class soon.....
1 gram of sugar will yield .489 grams of Co2
You have 25 gallons of wine roughly which I assume to start at 25 bricks which equates to 282 G/L sugar.
25 gallons is roughly 100 liters
The density of Co2 is 1842 g/m^3
So, take 282 g/l *100 liters *.489 gives you 13789.8 grams of Co2 Produced from the wine. Assume it creates that in 3 days so the wine would make around 4600 grams of co2 a day.
divide the mass of co2 by the density 4600/1842 yields 2.49M^3 of Co2 made per day.
Take the room size, of 500ft^2 and multiply that by a ceiling height of 8 feet to get a room of 4000ft^3 which is equivlent to 11.32m^3.
So looking at the air space to Co2 generated per day in theory the wine could fill up around 20% of the room with Co2 a day. However, another thing to consider is that a human (according to wiki) makes around 1.8m^3 of Co2 a day.
Thus ventilation is the key.. Also, something else to consider which is important is that Co2 sinks to the bottom, so still be very careful about sticking your head down to the wine and especially careful if you got it stashed somewhere like a closet.
Also, please don't use this math as a legit safety evaluation because it was done in about 15 minutes very shortly after I woke up, but just to get an idea at the numbers we are dealing with here. Also, the Co2 will not evenly disperse around the room, it will sink to the bottom, so you wont to be careful about that.