Konnichiwa, and thank you for your post.
First of all, I'd like to encourage you that you are making progress each day at a time. You may not feel like you are, but surely you are if you're doing all the things you've listed!!
I must say that even though Japanese is my native language, it can be quite tricky to explain the language.
It seems that you are doing all that you could possible do to improve your Japanese - and that's great! Subarashii! :P
It is always a great help if you can speak to a Japanese person - is there someone you may know?
By speaking what you have learned and listening to what they say - with a real person in real time - it is certain that your understanding will improve.
However, I know that sometimes this is impossible, depending on where you live, and what you do (no time).
A great way (which you have already found) to learn Japanese is through MANGA (cartoons). Japanese Manga contain short and witty lines that you would hear in any street of Japan.
In terms of learning how to read and write Katakana - post a Katakana table in your toilet!! So that every time you go, you'll be staring at them!! (I often find Japanese learners doing this... and funny enough, it has helped them.)
I'll let you know as soon as I come across a source that may help you in your studies.
Gambatte! You can do it!
- Sayaka :P