Firstly, I had to really look at your picture to find anything abnormal at all and even now that I've done that, idk if I'm even looking at the right thing. To me, it looks like something really minor. Think of it this way, you show up to your doctor with a small scratch/scar, what are they going to say? Some might even scoff at you. I'm not trying to be mean at all because I've had way more irrational thoughts than you are having..But I truly think that is nothing at all.
Secondly, I have basically all the other "symptoms" you are talking about! My lower back dull ache may be related to female problems..but still, I'm sure its nothing.
Thirdly, I have the knee thing. Mine always cracks, one more so than the other. My ankle and wrist also crack.
I also have two nodes right now, one is tiny and one is a bit larger but still small. I'm freaking out about it too but if you read here on the forum, TONS of people have nodes like these, some even more suspicious than the ones we talk about (eg clavicle and hard) that still end of up being nothing. Some people constantly have palpable nodes that are not even swollen and some people's nodes just never go down. If you've had a node for three years now, erase that from your worries list. Seriously.
Nothing you've talked about points to muscular cancer which is rare anyways...you are lumping in symptoms. You're cherry picking symptoms of awful diseases and applying them to yourself. Right now, I can diagnose myself with aids, lymphoma, ovarian cancer, brain cancer, salivary gland cancer, thyroid cancer, potentially leukemia and melanoma and going blind if I wanted to and thought about things the way google does.
I think you're alright.