Confused by outdoor light fixture wiring – two whites and one black

Hi folks. I’m attempting to replace a damaged light fixture on our outdoor (though covered) patio. I removed the old light fixture (power off at the breaker), and was surprised to find a few things:

First, that there is a single black wire along with two white wires twisted together. On the old fixture, the black was capped to the black wire from the fixture, and the two white wires were capped to the single white from the fixture.

Second, the smaller of the white wires appears to be bare (missing insulation) near where it comes out of the cable.

Third, the grounding wire on the old fixture was connected to a screw on the old metal mounting bracket (not pictured), however that bracket didn’t appear to be connected to any metal or grounding wire. It did have two screws which go through the holes on the left and right side of plastic box/mount shown in the picture. However, I’m skeptical that they are connecting to anything metal behind the plastic (though it’s possible).

Since this is a ~110 year old house, I think it’s possible this simply lacks a ground wire connection.

My questions are:

1. Why are there two white wires wrapped together – is this normal? I’ve founded discussions about setups with two whites and two blacks, but I don’t seem to have another black.

2. Should I be worried about the smaller white wire having bare wire exposed like this? If so, what should I do about it?

3. Do I need to be concerned about grounding?

This light is on a single switch and nothing else is controlled by that switch.

Thanks for any help you can offer!

Update:
Here’s a picture of the light switch (the one controlling this fixture is the switch on the right).

It has two wires coming from it. In the box behind the switch there’s kind of a jumble of things, but I see what looks like a small ground wire. So now I think the small white wire that’s partly bare at the fixture location may actually be a ground wire. Is there any way to confirm that? I do have a multimeter.

Is there any reason it would’ve been connected to the white (presumably neutral) wire like that?

Update #2: Adding a picture showing that the smaller wire is indeed coming from the same cable, but appears to be bare inside it as far as I can tell, further supporting the idea that this is indeed a ground wire.

Update #3:
On the switch side I see what looks like grounding wire(s) being capped together with a white/neutral. So perhaps this supports the theory that the neutral to the fixture was damaged or something so someone decided to abuse the cable’s ground wire as a neutral?

Here’s a photo of that, a little hard to see (ignore the screwdriver at the bottom that I’m using to try and hold some of the white wires out of the way).

Update #4:
Adding another picture of the switch side. This shows the adjacent switch which controls some inside lights. These lights are on a 3-way switch setup.

I see:
A cable in the middle which I assume comes from the breaker box. The black wire here is capped with two black wires, one going to each of the switches. The white wire from this is capped with whites going to the two outgoing cables on either side. However, one of those is then connected to the ground wires with the cap shown above. That includes the ground wire from the panel and the ones going to both the interior and exterior lights.

The interior light switch has three wires attached – I believe one black from the panel, one black going to the interior lights, and one white going to the interior lights.

Seems bad that all the grounds (not just the one for this fixture, but also the other fixture and the panel ground) are connected back to the panel neutral?

Thank you for the great help here, even though it’s not what I wanted to learn 🙂 I’ll be getting an electrician to come sort out this mess as soon as I can.