We've been having issues with our bathroom drains for a while now, and I keep puzzling over what could be happening. FIrst off, our toilet never has good water level. It will fill to the water line after a flush, but will not stay there. Also, it takes a bit of effort to get it to flush, it almost never will on the first try (it makes a squeaking sound?), the second try will be successful, but you must hold the handle down for at least 5 seconds. I have heard bubbling coming from the toilet, and seen the water level move drastically up and down, but this isn't common at all. I have only seen this happen a few times the past 2ish years.

Our sink and tub drain fine, but the sink is stinky after running water down it for a bit. Neither are slow. I suspect the vent is clogged somehow, or it could be that rubber octopus my son flushed down the toilet a few years ago! It was originally clogged, but I managed to get it down, could that still be in the line causing these issues? TIA!

Your toilet problem sounds like the guts need adjusted in the tank, and you may have a partial blockage in the stool or as far down as the stool hub. If the toilet is decent, it needs the tank trip lever or flapper chain adjusted, and the stool should be augured out with a closet auger. If it is a cheap toilet, you may be better off spending that money on a new stool. The stinky drain is likely to be gunk in the overflow or on the pop-up assembly that needs cleaned. If you know how to disassemble the pop-up, remove it and replace the rod and nut onto the drain body, then stuff a wet wash cloth into the drain, twisted up tightly to stop all water flow, just leave the excess sticking out, but get it at least 3 inches into the drain. Fill the sink up with hot water about half way, then add a cup of bleach and fill the rest of the sink with water. when it gets to the bottom of the overflow, I would personally add more bleach so that concentrated bleach water goes into the overflow and kills the bacteria and loosens the gunk buildup. The pop-up stopper can be cleaned with a paper towel and dropped into the bleach water to sanitize. Let it sit for about 20-30 minutes, and run water into the sink every few minutes to keep the level topped off above the overflow hole if possible. When the time is up, remove the washcloth, rinse the sink and drain with water, then reassemble the popup assembly.