Welcome to GMAT Club!
Sorry to hear about your experience but you in the right place for help.
It is interesting that you are so disparate in terms of your practice and official tests. Have you discovered the GMAT Prep Software yet? Is that what you have taken to get 630?
In terms of other overall thoughts/suggestions - Kaplan materials are not bad by themselves. I have used 3 of their books without
OG to go from 540 to 750 but i was very methodical about each chapter and step - I made sure I got 90% questions correct in each section/chapter and if I did not, then I went back and saved each question I missed, trying to learn, figure out the concepts behind them. Something to consider. It may seem like you have a lot to catch up at 480, so take it one chapter at a time...
I noticed you did not post your score distribution so I am not sure which area to recommend but in terms of Quant specifically, yes, Books or cheap online courses (under $100) are sufficient for most. I am old school so i like paper and lack of distraction/interactivity but others may learn better with web experience. Anyway,
MGMAT Quant books are great - there is quite a few of them. The whole complete package will cost ya $120-150 (including verbal ones) and they come with 6 tests if you buy the full package (so just get the full pack).
The only downside of this approach (using
MGMAT books) is it is a LOT of material to cover again, so you have to be committed to going through it.