So I bought this book by ALC (http://www.alc.co.jp/), intended to teach English to Japanese speakers, but packed with ~1000 sentences in Japanese that I thought seemed nice and would be fun to drill into as part of my building of a personal deck.

The problem is that the Japanese sentences don't have furigana so I will have to figure out the readings myself and that will probably consume some time, but I still thought it was worth it, I actually think it will be fun to plug my way into this material.

What do you think of this approach? Should I stop being so picky and simply go back to Core?

Honestly dude, it doesn't matter what you do, as long as you're doing something. That's the best advice I ever received, and I received it on this forum over a year ago. In the year since then I jumped around between different study methods, but have been keeping immersion to an absolute maximum. After the earthquake I even stopped doing Anki entirely for a while because I was talking to people and listening to the radio or reading the newspaper or whatever all day long. My ability went up better than it did on 8 hours a day of Anki.

What I'm trying to say is, it's all good. That book looks like a great idea. Embrace and enjoy learning the readings and meanings of the kanji without the assistance of furigana. Learning this language is a ton of fun, enjoy every minute of it.

Thanks for the good advice man.