You need to check with your doctor. He may want to see you. It may be that you need to change your type of therapy for a while. Sounds as if you may have injured it somehow. Don't take chances. Get him to look at it.

Cold weather makes a lot of breaks hurt! My husband broke his ankle over 60 years ago playing football. In cold weather, it hurts!! But not enough to keep him off the golf course. He just puts a support thingie on it and goes ahead.

You need to call and talk with your doctor ASAP. He will no doupt want to see and examine your ankle, do some xrays and see what's going on.
Sounds like you will also need some professionally done physical therapy. Guidance as to the correct exercises to do, how much to do and when to do them.
Swelling of your ankle is an idication of several different things and only your doctor can tell you what they are.
The fact that by evening your ankle is swollen and "throbbing in pain" says that something is not right. Could be too much pressure on the ankle to soon, not the correct exercises being done, additional damage to the bones from walking to quickly on it, and it could be that some or any of the hardware is coming out of the bone.

Remember that the ankle takes much of the weight of your body on it every time you stand on it. If it isn't healed enough when you put full weight on it, you can rebrake or hairline fracture the bones again.

As for the plate hurting in cold weather, that's not uncommon to happen. It may be possible in a few months to a year, to have the plate removed, but it's too soone to do so right now, I would think. Talk to your doctor about all these problems ASAP, before anything gets worse.
You should explain to him/her about your finances and see if your charges can be reduced. The same goes for physical therapy. There should be some arrangements you can make to lower the cost quite a bit, based on no insurance. It's worth a try, because it sounds like you will need some.

Good luck