Not a tax expert, but I believe you can save the entire $53K in a SEP-IRA. You should still be able to save the $18K in your employer's 401k program, and additional $6K if you are over 50. The $5.5k for IRA is subject to income limitations, but if below that value for 2015 then I would save that as well, most likely as Roth.
My logic is that these are two different income types. Unless there is an IRS limit for combined, or can take the max of one income stream, you can essentially save all of your side self-employed income.
Check with tax laws or a person more knowledgeable then me. Also a lot of good kknowledge on the board here so hopefully someone can contribute to this discussion.
I used to have a handle on life....... but it broke!
Semi-Retired 7/1/16: working part-time (60%) for now