Clod

if you want to know a way I tried practicing for getting rid of air through your nose, try and sing while pinching your nose, and adjust things until you no longer sound like squidward.

As for your throat, maybe put a finger on there and be aware of it moving. And try to avoid that as much as possible.

Overall, your not super bad or anything, the biggest thing you need is confidence, and also, when I sing songs, i usually run them over like as many times as possible, an...

*and you seem to have not run over this song before if not enough, so try to make sure you know the lyrics from memory basically, and practice a few times and get several attempts before getting your cleanest run.

Another good tip, drink lots of water, before, during, and even after singing! It's good for your vocal chords, and for you! Drinking things that are thick like milk and fruit juices increases mucus production, making it harder to sing.

Anyways, sorry for rambling, I enjoy sharing my knowledge of singing, as I love singing, but even I have a lot to learn, I have never even taken lessons for singing, I've simply learned this from tips and stuff from others, and even online. So i'm not like a professional or anything, and still have a lot to learn, but hopefully this stuff will help you, because many of it helped me! Good luck! And trust me, you don't sound as bad as you think!