Hello dude.
Man, I think you are being over distressed for nothing. I will tell my way of thinking and how I do things.
Like many other solo devs here, I purchased almost every asset used in my game (except some free ones) from many marketplaces, includind turbosquid.
So whenever I purshase some asset, I know I am doing the right thing in a moral point of view, because besides the legal trouble of “stealing” other game’s assets, I think it is immoral you use another person work without paying respect to him/her, using their work without authorization.
After I purchased the asset, after I payd for it, I use it however I want, I don’t care if the author says it must be used this way only, and not that way. I think I am not cheating, because I paid the price for that product, so now I can use it however I want. Just like when you purchase a car, then you want to make it a mobile fast food truck, to earn money from it.
For every asset I purchase, I change it completely, I change the texture, some model details, until it becomes unrecognizeable from the original asset, and let’s be realistic, there is absolutely no way to distinguish in example, a general AK-47 rifle of one game from another, because they all look identical.
I do the same with character models, I purchased many soldiers, terrorists, and so on, then I make changes on these character, on their textures, I even mix body parts from ones to anothers, so this way I can make these character look unique, and not just a generic character from marketplace.
My last words, don’t overwhelm yourself with these small detail, once you paid for the model, use it however you want, and change it, so it will not look like the original purchased asset.
Cheers and good luck