Good luck on your self-publishing journey! If you haven't, join as many self-publishing forums and groups (on Facebook, etc) so you can get as much info and knowledge as you can. It will make everything easier.

As for your plan, I am confused as to why you'd want to submit to small presses now that you've decided to self-publish. I understand you have some time before your release but you might be better off writing other things so you can get stuff out there. The catalog and back list is an important tool in self-publishing so you want to have as much work out as you can so you can build loyal readership. Instead of waiting for October, you could start on new work (if you haven't yet) and then when you publish in October you will have other work already done that you can get out there.

If you only will have one book out it's going to be hard to gain traction and even promotion won't help much with one book. Readers will want to funnel to other books so you wanna have get to building that catalog. I'd concentrate on that because I can't see why you would want to submit to small presses at this point. As others said, there is nothing they can do for you. Most do not have the money or resources to get you decent sales, you most likely will not make much money at all, and you won't get promotion beyond maybe a tweet or FB post if that, and then you might end up not being paid, etc. Also, your books might be extremely high making it hard for you to compete.

If you are self-publishing, then give yourself the best shot. I would work on building my indie business if you intend to self-publish long term. Put your energy into that if that's what you want to do.

Good luck again!