Yes, Chinese would be VERY helpful for kanji. Back when I could read a lot more of it, I remember trying to figure out a martial arts book, and a friend's Chinese friend saw some of it and was able to explain it to us (my friend couldn't figure out either, and he was really well educated). I forget the exact figures, but I think for Japanese, you should know about 2000 to be literate whereas in Chinese, it's more like 5,000. When I was learning, it was before computers, and I think I could write a couple of hundred. Nowadays, my wife and her friends say they can read just about everything, but are so used to using computers that they find they cant write a lot of them that they once knew.I learned Hiragana and Katakana back when I was into AnimeStopped at Kanji though, but I'm more interested in Chinese nowadays so maybe that'll be helpful for Kanji later.
My mother in law, a Hiroshima survivor, (she was 13 when the bomb dropped), could when we first met, sit on a bumpy bus and write perfectly vertical lines of kanji, on unlined paper. That was probably 25 years or so ago--she's in her 90's now and I doubt she could still do it, but to me, at least, it was REALLY impressive.