Solo 401(k)'s to defer gambling income?

Has anyone considered a solo 401(k) to shelter their gambling income? According to this article, a solo 401(k) allows a self-employed person (with no employees) to defer taxes on $14,000 + 20-25% of the rest of their self-employment income. This would be perfect for me, because I have a day job that pays for all my expenses. My poker income will be around $15,000 this year and I've mostly invested it in the stock market. I had planned on saving my poker income for retirement even before I found out about the solo 401(k).

Here's my questions:
1) Can gamblers who file as professionals take advantage of the solo 401(k)?
2) Can a person have both a 401(k) at their day job and a solo 401(k)?
3) Is there a max-contribution limit for the two 401(k)'s combined?
4) Are there any income limits?
5) Are there any good books on solo 401(k)'s and like plans?

I'll probably pull in around $60K from my dayjob this year if that makes a difference.