I can't answer your question about when to submit this cycle, but I can tell you my situation (take with a grain of salt).
I actually had a very similar undergraduate GPA over 5 years (had an entire year of Fs due to an extended absence and being an all around fool not realizing I should've left school and sort my life out) and also a 29 MCAT as well. Following graduation I took a year (8 courses) of UDV Bio courses and got ~3.9. I also retook my MCAT and got a 519 (131 BS, 131 CARS, 129 PsySoc, 128 PS), all-in-all submitted AMCAS by the end of August.
I applied narrowly to local schools, expecting to re-apply the following cycle, but scored 3 MD IIs and 2 Acceptances (granted one of the IIs was merely a "courtesy" thanks to a favor from a friend, and I didn't get in anyways. One of the acceptances was also my alma mater, which I had 2 LORS from their med school professors).
Since you seem intent on applying this cycle, if you really do as well on the MCAT as you think you will and are going to the SMP I think you're going to I imagine you could get in there unless you're a terrible interviewer. If you don't do as well on the MCAT as you intend then, welp, it'll probably just be money down the hole.
Best of luck!