if someone could point me to a solid book or site to get started, that would also be lovely.
Stick around the MMM forums and you'll get some good general tips. Wikipedia has many great pages, such as
this overview of 401k and IRA rules.
Bogleheads wiki is great for investing advice. I'll spare you more links because there are plenty further on in my post.
I currently put 7% of my income in pre-tax 401k through my company. This gives me their full match (3.5%). I project to have $400k in this account by 43 and $1.5MM by 65 if I cease contributions at 43 and earn 6% interest after that. This is enough to fund post-65 retirement, and I also should get a very healthy pension, so I don't wish to contribute more to accounts that I can't access until 65.
You can take early distributions called Substantially Equal Periodic Payments (SEPPs) from a 401(k) by following IRS rule 72(t). Plug your numbers into an SEPP calculator like
this one to get an idea what sort of income your account could provide with that method.
Alternately, you can convert your 401(k) to a Roth IRA in the year in which you leave employment. Roth IRA principal can be withdrawn at any time without the 10 percent penalty, but if it comes from another retirement account you'll have to let it season in the account for 5 years first. If you choose this method, you'll have more access to and flexibility with your savings than if you take 72(t) distributions, but you'll have to come up with a way to fund the five years between when you retire and when your 401(k) money is fully seasoned.
I plan to save >$25k/year above and beyond mortgage (3.5%), 401k, Health Savings Account, Daycare Flex Spending, 529 College Savings, and Student Loan (3.875%) payments.
If you find one of the two 401(k) early access methods fits your situation, I would encourage you to up your 401(k) contribution to the maximum, $17,000. $5,000 more should go into an IRA, and since you're planning on retiring early that IRA should be a Roth. This will minimize your total tax burden: the least tax-advantageous investment is a regular brokerage or mutual fund account, like you would open with Vanguard or Fidelity, and if you're putting your money in tax-advantaged pots first (Roth IRA, 401k, mortgage paydown, student loan paydown), you bear the full tax burden on much less of your income.
I project that I will make $30k/year interest on this extra investment after 14 years if I earn 6% return.
These are my basic plans. I realize that 6% may be a little optimistic, but that is how I did it for now. I can adjust things accordingly if I change that.
MMM (and much of the ER/FI community)
suggests using a 4% SWR to adjust for inflation so that your buying power won't erode over time.
My work's pre-tax 401k is through Fidelity. I can also contribute to a Roth or an after-tax option.
If by this you mean a Roth 401(k), that might be worth looking in to; Roth 401(k) money is easier to convert to a Roth IRA than traditional 401(k) money is.
Honestly, I'd just like to invest my money is several diversified index funds across stocks and bonds, and not pay gains taxes until after I begin using the money after 43. Is this possible? Or will I always be paying gains taxes as the interest is reinvested no matter what path I take?
My eyes, they burn. But seriously... 401k and IRA money aren't affected by gains taxes. You only pay on the Roth accounts when the money goes in, and you only pay on traditional accounts when the money comes out. It's only for your last pot of money, the traditional brokerage account, that you've got to worry about capital gains taxes and taxes on your dividends (which I believe are taxes as regular income, not as capital gains, but that nugget is worth what you paid for it.) You can also arrange your funds in various accounts in order to be the most tax efficient, a topic that
the Bogleheads wiki covers very well.
Should I be contributing to a Roth, knowing I want benefits from this investment at age 43? I've heard there are loopholes for accessing this money without penalty. Is this true?
The only withdrawal penalties are on earnings, not principal, and there's a principle that you withdraw principal before earnings, so it's only after you've withdrawn all of your contributions that you have to worry about a penalty on withdrawals.