For the things on your list, here’s my approach!
Underwear: I’ve heard of people turning old underwear into rags for stuff like washing windows or glasses since the fabric tends to be very soft! Or just rags for any kind of cleaning since it doesn’t matter if it gets gross. Personally, I’ve used the cotton jersey out of my old underwear and sewed them into soft cotton pads to apply skincare - maybe a little ick for some people, but I washed everything in boiling hot water so I know it’s sanitary at least. I also keep the elastic bands for other sewing projects, but I’ve heard of people using them to help with cord management or other scenarios where you need to tie something. Lastly, cotton underwear is better for your body anyway and biodegrades much faster than polyester, so I try to only buy cotton if I can.
Toilet paper: I try to buy bamboo toilet paper if I can. I am not brave enough to try those reusable wipes that hikers use, but they do exist… otherwise, I just try to buy as responsibly as I can and move on.
Tissues: I avoid tissues entirely! I have a selection of soft, old handkerchiefs that I got for dirt cheap at a church thrift store! I’m not kidding, they were all 50 cents. Before we had disposable tissues, we had handkerchiefs, and they’re not as gross as you might think - you can blow your nose and then fold them up so the snot is tucked away on the inside (though I’ll be honest, sometimes when I’m sick or crying, I do just throw the handkerchief directly into the laundry after using). You can also boil them to sanitize them. On the rare occasion that I’ve bought a box of tissues, I did hang onto the boxes to use for organizing drawers etc.
Menstrual pads: I made a post recently about DIY reusable pads (plenty sanitary, don’t worry!), but there’s also options like Diva Cups and period panties. That said, for a disposable pad (or tampon)… I think the best thing we can do is toss 'em and move on. I know there’s brands who claim to be better for the environment but I don’t know anything about that.
TL;DR: reuse it somehow or use an alternative that doesn’t need to be thrown away
I’m with you on this one. So many scenarios in which someone might want to buy just one/one quantity of something, separate from all the rest… I think we should put more pressure on businesses to use non-plastic materials (or at least more biodegradable plastics) and encourage returning those containers to the company for reuse.
You don’t need to inform them…