I'm hoping the video you watched was our own Tammi. Here is a link to her wonderful videos.
https://www.youtube.com/watch?v=kzFX...AyBQ2l-Mzkw7ew
I'm not sure what is going on with your tension but a little bit of something or a burr that snags thread can put things out of kilter. It kind of sounds like it isn't put back together quite right. I know the first time you do one it can be a little scary. But take it apart and get all the rust out. Watch/feel for burrs. A short soak in vinegar might get some rust off loose parts but I wouldn't put any vinegar on the machine. If you soak too long it will rust it more. I've had luck with bicycle chain oil. It has a detergent that works on the rust. I wouldn't use it anywhere there isn't rust though. It is kind of heavy. Be sure to put it all back the way Tammi shows on her video. I think she has another video similar. If you post more questions here she most likely will reply here.