If the OP wants more, he will need a bit of calculus. But even for this, I don't think he'd need anymore than single variate.
If the OP can, for example, can match molar quantities, chemistry experiments should be able to be skipped.
Have you ever tried to independently learn this stuff?
All the time. In fact, most science majors and students do a lot of self learning. A chem professor I had always said, "Don't let your courses get in the way of your education."With youtube, free books, and edu websites, it's especially true today.
What should I read/watch/listen to?
EDU sites. Youtube. You can literally type in a question or a topic and find good explanations.
Any good websites you can recommend?
Already recommended: khanacademy. Hyperphysics.
Where should I start? What are the key/basic concepts I should try to learn?
In my opinion, students should start from physics. I feel physics teaches you to quickly learn all the sciences. Chemistry itself virtually fell out of Quantum Mechanics. Thermodynamics are better explained by physics, although overlap occurs in Physical Chemistry and Chemical Physics. From understanding basic Newtonian Physics, you can understand a good deal around you.
However, physics is more math heavy than chemistry. BUT it explains the math better. I took several physics courses because they made the math I was doing much more concrete. IMO, Physics I at a university does a better job at teaching calculus than actual calculus courses.
How much math do I need to know (I have a vague memory of 11th grade math)?
Basic Chemistry - Algebra 2
Organic Chemistry - none
Biochemistry - depends. Could be just algebra or up to very in-depth calculus and linear algebra.
Physics - depends. You can do it at an algebraic level, but the calculus versions give you more understanding
Biology - depends. Genetics relies on a good deal of math.
I recommend learning something like Organic Chemistry first if math is the issue. For one, it explains things you're used to seeing in your products everyday.Secondly, it builds spacial intuition, which is useful in all sciences.