Wow, that was an interesting way to start your career in self-publishing.
You have received lots of good advice already. To add to the excellent suggestions from Lemurion concerning self-editing, try using some text-to-speech software to read your story aloud. The computer will always read what's there, your brain won't, and having it speak the words often helps to identify missing or out-of-order words. Not only that, good text-to-speech software can help you discover rhythm problems in your text - sentences that are too long and complex and so on.
Note that, when resorting to self-editing, it is not a matter choosing one of these methods, but using them all. ... And, as already pointed out in that other thread, this will only work if you have the knowledge to identify the errors.
None of the above really makes up for not getting a professional editor, but if that is not an option then you must be willing to put in the effort (and proof-reading four times won't impress anyone
).
As for submitting to Amazon - definitely go direct.
As for price. For a first novel of this length $3.99 is as far as I would go, but you will need to market heavily and offer coupons for free access and so on, especially early on. Don't get your hopes up too high.
There was a suggestion that you might consider splitting this long novel into two or three shorter ones - priced accordingly, perhaps even making the first book free. IF the story lends itself to this, then it is an excellent idea, but readers will get annoyed if your first book doesn't arrive at a satisfactory conclusion. (It can still be obvious that there is more to come, but a cliff-hanger at the end of your first novel will turn away many readers unless the story and writing so far has been truly exceptional.)
Note, too, there is a big difference between free with a coupon and permanently free at Smashwords. Permanently free books can be downloaded without registration, and as such they tend to get downloaded much more often - but it is anyone's guess if/when they actually get read. Free with a coupon on Smashwords only works for registered users and will not get as many hits - and it's still anyone's guess as to when the books may be read. Many download while the books are free, and it goes into the virtual pile where it may or may not ever be looked at again.
Marketing is not something I'm good at, but if you hope to see any interest in your book you need to hunt around for suitable reviewer websites and try submitting with them (follow the rules they will have on their website).
Finding readers is hard work. Marketing, and making sure your preview and presentation doesn't immediately put people off by it's lack of professionalism (lack of editing etc.), are critical. And whatever you try, it will remain an uphill battle just to get people to pick it up and start reading.
In the end: success in writing is about being in it for the long run.
It is very unlikely this first book will earn much, if anything, at all. Be ready for that. Do what you can to make the best of it, you don't want it to be the sample that means no one ever looks at your writing again, but after doing the best you can ... move on.
What Hugh Howey refers to (on his website) as your "breakout book" may not come until the 10th book or even later - if it comes at all. So you need to keep writing and keep publishing. (
Do NOT follow my example and let years go by between books .)