I'm on Linux, so played using Wine. It seemed to play fine.
The thing that I think is most needed, is a bit of instruction on the rules and controls. I see that using A and D are in the devlog, but I read that earlier and forgot by the time I played. There is nothing in game, nor on the main game page, mentioning them.
You talk about keeping an eye on Reginald. Is that related to being able to change your position? Is it that you can move for a better viewing angle, but if he is not in your field of view he may cheat? Or can he cheat even if you see him? Is there any way to actually counter his cheating? Can you catch him? Can you prevent it? If the system is that he may cheat at any time, but especially when you are close to winning, and there is nothing you can do about it, then no, it is not fair or fun. There has to be some gameplay element to it where you can have some control, even if it does favor the computer cheating. Having to take all your shots while keeping him in view is limiting, but would at least give some control. Of course, if that is the case, then he should be moving around. This will both give you a chance to get different angles, but also can't rely on staying in any one place.
It took a bit to get a feel for the shooting controls. I had missed, or not remembered, the devlog comment on the A & D controls, but eventually did find them, and they were a big help. I got down to 2 balls remaining. I think he was at 3 or 4. Then he cheated, adding more balls. After this I tried to keep him in view. There was no more cheating, but I also was not doing as well.
The physic feel fine. I don't do a lot of pool games, and the viewing angles were a bit limiting, so it is hard to tell why any shots missed. It could be physics, or it could be I wasn't lined up as well as I thought. I think full 360 degrees of rotation would be nicer for lining things up, but the current system isn't too bad. If this was going to be a full standalone game, I'd say it needs the full freedom of movement, but for a mini-game, the current way works.
The delay at the end of a turn feels a bit long, and could potentially be shortened. It feels like it might be waiting on the physics to fully stop to see if any more balls will sink, but when it looks like nothing is happening it feels off.
The bits of dialog work well and give the character some personality. The animations also fit, and I like how he is mostly waist up, and often floating above the table.
Overall, this feels like it would make a good mini-game.