@Tee213 Personally, I don't think lowering your price is ever appropriate. You sound like someone who isn't going into this blind- you've done your research and know what similar places are charging. You'll likely put your price up during holidays and events and lower it during slow times, but that's your decision, based on what the market will bear, not for a guest to dictate.
If you spend some time on these forums you will learn that guests who start off asking for discounts, for you to bend your rules for them, or anything else of that nature, end up being problematic guests. Red flag guests. You found that out for yourself already and it won't change. By asking you to accommodate their budget or needs, rather than looking for a place they can afford and houses the number of guests they want to book for, they are showing you that they are disrespectful and entitled, and this won't change during their stay. And once you make exceptions for them, it emboldens them to expect even more special treatment.
The only time I would think it appropriate to make a special price offer is if you had a guest who had already stayed with you, you found them to be a great guest who you would welcome back, and they wanted to come back for an extended period of time. Then you might offer them a special price if you felt like it.
That guy you got who brought more people than he booked for, wanted to get in early after a last-minute booking, and who you gave a discount to seems like a real piece of work. He claimed he didn't want to bother you during the stay, because he didn't want to seem like a complainer, then wrote a public review full of complaints. It's really too bad he mentioned in his review that you gave him a discount, as that will encourage future guests to ask for that as well. Just answer guests if they ask about that, something like " Yes, I did offer one guest a discount when I first started hosting, as I wanted to attract guests, but now that I am established, my price is firm and in line with what I offer."
And Tee, never write, as you did, in a public response or a review that you reimbursed a guest for a non-working appliance, or anything else. By doing that, you are just setting yourself up for future guests to come up with complaints, expecting a refund. If thre was something not working and the guest mentions it in a public review, your response should just make it clear that you did attend to it ASAP, it has been fixed, and that it is no longer an issue.