Secondary questions

I'm working on my first batch and have just racked it into secondary. I've got a couple questions about it:

1) I made a 2.5 gallon batch and am using a 3 gallon carboy. After racking to the carboy it looks like there is actually about 2 gallons instead of 2.5. (I'm guessing this is cause the markings on the bucket aren't really accurate and because I left a bunch of stuff behind when siphoning.) Is this extra headspace in the carboy an issue?

2) I kept my house around 74 or 75 degrees while the beer was in primary. Now that fermentation is complete do I still need to keep the same temperature? I usually have it around 76 - 80 during the summer and would like to go back to that as soon as possible.

Thanks

Head space is not an issue. Every time you move your beer you knock the CO2 out of suspension and it blankets the beer to protect it.

Once it's fermented, temperatures are not as much of a problem. Next time, get a large tub that your primary can fit in. Fill the tub with water and put a to t shirt or towel around your primary to wick the water up. It will help keep your temperature of your primary down during the summer.