You can see light at any range
I did some googling, and while it's pretty hard to find specific citations from scientific studies, the places that I've been able to find say that the human eye can see a candle from somewhere between 10 and 30 miles away. The curve of the Earth is about 3 miles away. Thus, any significant light is at least barely visible from any range that you're likely to have line of effect. The houserule that I've used for a while now is that you can see a light source at ten times the distance that you can see a non-lit object without penalty.
That said, the vision rules in every edition of D&D that I've seen are actually reversed. They only work if both the looker and the looked-at are in the same lighting conditions. The vision rules on PHB 183 state:
In a lightly obscured area... creatures have disadvantage on Wisdom(Perception) checks that rely on sight.
A creature in a heavily obscured area effectively suffers from the blinded condition.
Nothing in those rules says that you can't see a creature if that creature is inside darkness and you aren't. This is clearly ridiculous. This weirdly reversed rule has existed since at least 3.0, and shows how little the designers thought about what to do about differing light conditions.
What this means is that you should rely on your intuition more than the rules for what will give penalties based on vision. Since, IRL, lights can be seen from the horizon, you can probably see someone with a torch from at least a few hundred feet, probably out to a mile or so.
As far as being blinded is concerned, my intuition was always that that penalty happened because you couldn't see the ground beneath your feet, or the things that are around you. Thus, I would rule that a character who can see a light hundreds of feet off is still blinded, except for the purposes of making checks or attacks against targets who are lit up.
There are no existing rules that explicitly allow this. The only methods of disarming that exist at present are the Battlemaster Fighter's Disarming Attack, and the variant Disarm rule in the DMG. Disarming Attack only lets you force a creature to drop an item that it's holding, not one that it's wearing:
When you hit a creature with a weapon attack, you can expend one superiority die to attempt to disarm the target, forcing it to drop one item of your choice that it's holding.
The variant Disarm rule likewise only lets you knock items from a target's grasp, not from their body (page 271 of the DMG):
A creature can use a weapon attack to knock a weapon or another item from a target's grasp.
If a player wanted to do this, it would presumably be either a Strength or Dexterity ability check, albeit a very difficult one.
Best Answer
Effectiveness of such an action should be resolved by an Ability Check.
While you are right that kicking a small object is a Free Action in combat, that doesn't mean you always succeed automatically. Sure, simple, trained actions like drawing a sword are not rolled for, but if you want to achieve a specific advantage with such action, you have plenty of interesting skills to choose from.
Most obvious would be to use a Strength check (Athletics) or Dexterity check (Acrobatics?), depending on your players description of the action. You could then place appropriate modifiers reflecting the terrain (mud, wooden floor, grass?), difficulty (Sword of Spiky Mistakes or Club of Harmlessness?) and other factors. Then, depending on whether the outcome is high medium or low you can adjudicate an appropriate distance.
Don't overthink this
Of course, the rules say little about such situations, but how many times do you imagine your players will kick something in combat? Stick to well-known simple systems and invent house-rules only if they don't work. It's more important to give a quick ruling and move on rather than ponder on what would be an accurate simulation. Treat it like a "miscellaneous" situation it is and go forth with the adventure. If your players complain, talk about the matter between sessions and decide on some rules that work for everyone.