Try a nettti pot for your sinus. It could help with the taste and brush and scrape your tongue. The taste buts can renew every two weeks maybe if you excite a refresh it may help. As for the poop smell it maybe chemical stay away from anything that can give you heartburn or GERD for a while and maybe fast with some tummeric tea for a day or two.
Hmmm… you said you haven’t had COVID … that you KNOW of. Does that mean you were not tested? Your description of tastes & smells sounds a lot like the descriptions of some folks who had COVID. I’d suggest you get tested, but if you already had it (maybe a mild case) & recovered, you might test negative. You can also get a COVID antibodies test - that would tell you if you ever developed antibodies to it, in other words, if it’s positive, it would mean you did have it at one point. I’ve heard many ppl who had COVID had continuing prblms w/ taste & smell long after they were over it. Good luck to you & let us know what’s found…