A minimum of 4x8 feet for an adult.
Most torotise care info you find will be old, out-dated and wrong. Here is the current and correct info, including enclosure size and type:
I don't think a single heater of that type will be enough for a NJ winter. Your thermometer will tell you.
For a temperature probe that you can access though wifi, I like the "Temp stick". @Markw84 uses and recommends the "Sensor Push". That one is cheaper but its only blue tooth. To use it...
Tortoises should never be housed in pairs. Groups of juveniles are usually oaky, but not pairs.
If you do get more, be sure to observe a lengthy quarantine. At least several months.
What size tortoise and what size enclosure are we talking about?
Tortoises do not hibernate in summer in warm weather. Hibernation is for escaping cold weather.
What species are we talking about? Size and age? Where is Winchester? The photos Blackdog suggested will help up to help you.
Don't switch to soil. Many people get sold the wrong heating and lighting stuff. The coir is a good substrate, but yours looks to dry and dusty. Read this to make sure all your care and lighting is correct...
48 x 30 should last about two years for a single or a trio. I'd never recommend a pair. I find it works best if you have a large outdoor enclosure to use during warm weather too.
I get the 96x36" ones and divide them in half for babies. I use the 18 inch tall ones because I stack them three...
Those are definitely a mix. The three on the left tell the story. An unscrupulous breeder might only show someone the three on the right and falsely claim they are pure. The bottom right one is unusual, but I could be convinced that the three on the right were pure. Especially the middle right one.
No one can predict this. There are many factors that will determine the outcome. Depends on the male, the females, the enclosures, temperatures, their mood, the weather, etc...
If you do get a male, don't skip the quarantine process.
You definitely want a closed chamber. Venting is good, but too much venting is not. The idea is to contain the humidified air inside the enclosure. Too humid? Open up the vents and lets some humidity out. Not staying humid enough? Close up some of the venting. In practice this is very easy.
Most of the people selling "pure" ones aren't. And they get mad and defensive when this is pointed out. I tried to tell the admins on a certain marketplace site, and they essentially told me: Too bad, so sad. Buyer beware.
Its not just two dots in every single vertebral. There can be one spot...