Series 79 Study Material: Questions and Concerns

I've been prepping for the Series 79 using the Kaplan textbook and Qbank. The textbook obviously isn't the best— I've noted a fair number of obvious spelling and grammar issues + it seems incredibly cursory in certain areas. There's also massive discrepancies between the knowledge being tested on the Qbank questions and what's actually contained in the text.
Furthermore, I've even noticed discrepancies within the Qbank itself (Ex: back-to-back questions with answers contradicting each other), which only heightens my concerns about relying on both of these resources as my primary materials.

Internet research hasn't assuaged my fears either...I've seen a fair number of posts from people claiming to have failed their S79 using Kaplan, including a damning Amazon page for a much older version of the Kaplan textbook (I can't post the link, but it's the second non-sponsored hit if you Google "Kaplan Series 79").

I'm already aware that Knopman is the preferred/recommended study prep course, but it wasn't an option due to the price point.
So my main question is this: If I was to supplement my Kaplan textbook with a secondary text/course, what would be the best option?
 

Currently under consideration are:

• Solomon Online Study Guide (and perhaps the exam simulator, although it's quite pricey)

• Securities Institute of America Exam Study Guide (I can't find much in the way of info/reviews for this one)

Any and all responses would be appreciated- Thanks!