#1 What do I do with all my cash, and future cash?
1a. $5k into an IRA per year seems to be the next best thing I should do. I'm fairly certain I'm over the normal limit for a Roth IRA, should I do a normal IRA or this fancy "backdoor Roth IRA" I've been reading about?
You make enough that you're in the 28% bracket even after all your deductions, right? (That is, AGI at least $85,650?)
Now, with a Roth or Traditional retirement vehicle, you're only paying taxes on contributions once, and so you only need to determine when you want that to be. With a Roth IRA/401k, you're paying taxes before you contribute the money, so the contributions are taxed at your marginal tax rate while you're working. For you, that's 28%.
With a Traditional IRA, you don't pay taxes on the money you contribute, but you do pay taxes on the money when you withdraw it in retirement. So it gets taxed at your effective tax rate in retirement. For you, the retirement effective tax rate will be much lower than 28%, so it's probably better to contribute to a Traditional IRA. As velocistar points out, your earnings disqualify you from deducting your traditional IRA contributions. Depending on your MAGI, you should either contribute directly to a Roth IRA, or if that's impossible contribute to a Traditional IRA and convert it.
1b. After maxing an IRA (I assume I can only have one at 5k/yr) and maxing my 401k to $17k, I have no idea where to best invest my remaining income (estimated $45k)... help?
After you've maxed your 401k and your IRA, you should contribute to a regular brokerage account at Vanguard (or somewhere else, if you prefer, but Vanguard is the one many like here). There will be no favorable tax treatment, so it's best to contribute only after the other two are maxed.
#2 My employer recently began offering a Roth 401k. Should I put some, or all of my 401k contribution into the Roth 401k, and will my employer's match end up in the normal or Roth 401k if I do so? From what I've read it seems I should just stick with traditional, but I'm not sure if one works better with early retirement.
For the same reason that a traditional IRA is better for you, a Traditional 401k is better for you. (For the record, if you contribute to a Roth 401k, the company pays your match into your traditional 401k.)
#3 Should I change my existing 401k distributions? I think having 21% in my company stock is too high, but if I take it out where should I move it to? Some or all to VINIX, as MMM seems to suggest?
Having anything in your company stock is too high. It's only a good idea to have any if you're eligible for a discount via an Employee Stock Purchase Plan, and even then you should sell the stock as soon as you can do so without penalty. By owning your employer's stock, you're doubling down on risk because your income and a fifth your assets are all in the same basket (your company's continued success). You may do great work, and your company may be well managed, but everyone thought Enron was a stable and well managed company in September 2001, didn't they?
As far as your overall asset allocation: I'd recommend you read
The Intelligent Asset Allocator if you want to be thorough, or the
Bogleheads start up kit and especially the
Asset Allocation determination page if you want a quick and good enough understanding of the issue. In general, you will receive optimum overall returns by spreading your portfolio out among several asset classes (stocks, bonds, real estate), and your risk tolerance will determine what ratio of these you hold (and what types of each, for that matter). In general, early retirees can afford to retire a year or two later or make big lifestyle cuts that older retirees can't, so they tend to have more tolerance for risk. If that applies to you, your portfolio could be relatively heavy on stocks (at least 70%, as high as 90% depending on your disposition) and light on bonds, and your specific picks within each asset class can include more risk (like small-cap and international stocks, for example).
You should also be considering your asset allocation across all your accounts when you get to the point that you have others. Your asset allocation is the set of rules for your portfolio as a whole, and it's generally not best to have each account contain an even ratio of each asset type. For how to place your funds best in the ecosystem of your three different accounts, check
this article out.
#4 Assuming my target retirement age of 34 works out, do I have to structure my current investments in a certain way in order to have access to enough dividends/income to pay for living expenses?
Most sources of information on investment and retirement are not based off early retirement, so I don't want to mistakenly put my money somewhere where it won't help me until 60.
To use retirement funds before 59.5, they have to be in a Roth IRA, and they have to have been in the Roth IRA for at least 5 years. In your case, when you retire in 2019, you'll move all the money you need to cover your 2024 expenses from your traditional 401k and IRA to your Roth IRA; in 2020, you'll move 2025 expenses, and so on. Each year, you'd pay income tax on the amount of money you rolled over (remember, money is taxed before it goes into Roth accounts).
To cover your living expenses from 2019-2023, you can use money that you contributed to a Roth IRA during your working career (this is an awful idea for you because of the tax implications), you can earn income with side jobs and consulting, or you can use money from your brokerage accounts. The last option is a great fit for you because you'll be contributing to a brokerage account anyway.