Caliper upgrade???

Having had several /6 Darts back in the day (and not sparing any of the few HP they had!), the standard front discs do quite well, so you will be fine. They have decent heat capacity for repeated stops, etc. I'd put any limited budget into reworking the whole brake, suspension, and steering systems rather than an upgrade.

Yes, on wheel bearings and races. Thay may be fine or may have a bit of rust and moisture in them. These are cheap anyway.

Since you say the front brakes do not work, that is worrying with the wife and child in the car (oh, and you too! LOL), soooo, other things to consider:
- Are you working on the rear brakes too? I tend to do the whole brake system stem-to-stern for an older car; the moisture that gets into the system effects each and every part, and you'll usually end up replacing everything in the the brake system eventually on a car this age.
- I'd replace the master cylinder too; you're gonna be bleeding it all out anyway so why not. Being this old, it may spring a leak at any time, on your carpets or between front and rear systems.
- And FOR SURE, all 3 of the rubber lines (2 front and 1 rear). They deteriorate on the inside liner first, where you cannot see it, and a chuck will fall out and lock that caliper or wheel cylinder, either off OR hard on.
- Any rust in or through any hard line is an unknown so it is hard to say what to do there; it would be reasonable to keep the hard lines, IMHO, if you are in a dry climate. If you are in the rust belt, then new hard lines are a very good idea.

FWIW: The front end kits are not something I would buy. I'd much rather go to the local NAPA store and buy individual parts. The price of the kits is no bargain, and you have less control over the parts that way, and a lot more hassle and a week+ of time wasted in getting a part exchanged if something is wrong in the kit. Either way, you will be glad you did the front suspension parts, despite the work involved!

Make sure you do all the steering linkage at some point; it is easy to do with the suspension parts: tie rod ends, idler arm, and look hard at the pitman arm joint; any motion there calls for replacement, even though it is a pain. And then there is the steering box and any slop in it. Do you have manual steering?

I know, this all adds up to a LOT. You will spend some dough doing all of this, but it will be up to snuff safety-wise, and you won't have to worry about these parts again for many, many years, and you won't waste tires from things like bad alignements.