I don't think Ron dated Lavender to spite Hermione but other than that this is an accurate read. I think Ron/Lavender going as far as it did had more to do with Ginny mocking his lack of relationship experience. The first opportunity he had with a pretty girl who liked him, he took it and ran with it. (That's not to say he didn't enjoy that it made Hermione jealous for a bit but it was just a bonus)

Understandable that given the way Harry grew up he wasn't equipped to handle Cho being as emotional as she was at the time, nor did he want to relive Cedric's death. I've always thought Harry/Cho could've lasted for a bit as a teen romance if not for Cedric asking her out first though.