What's your asset allocation? Without knowing what you are comfortable with, it makes it a bit harder to make suggestions.
BUT the fact that you've got your investments currently going 100% into the Fido 500 fund which is 100% stock/equity, means you might be comfortable with volatility? Or you're not watching the market so you're not seeing the ups and downs and therefor might still be okay with 100% stock allocation?
The fund you've got currently selected is fine. Fidelity 500 Index Fund (FUSVX) has an 0.045% expense ratio which is great, and will be the closest thing you have to a index fund out of all the choices available. Shame they didn't include the Fidelity Total Stock Market Index Fund (FSTVX) but the 500 is still great out of the rest of that group - and you could ask the plan manager to consider includig the FSTVX at some point!
As far as what you have in your old 401k, you should probably get out of the Vanguard and other fund as they'll be charging you there own expense ratio for managing that fund in addition to whatever the funds themselves charge, which isn't a huge amount considering, but still no reason to pay anyone a penny more than needed of your hard earned money.
In your Roth, the Vanguard VTIVX is a target retirement fund that rebalances automatically meaning it will start out heavy in stocks and light on bonds but as the target date gets closer, it switches the ratios to be more bond, less stock so you get more stability right when you need to start drawing off of it. Target date funds aren't bad, but they do tend to be more expensive than just doing it yourself - buying say 70% stock mutual fund and 30% bond mutual fund and then in 5 years changing it to be 65%/35% and so on... it is MUCH cheaper to just do it yourself in terms of expense ratios. But since it isn't a native Fidelity fund, they'll charge you to own it. If you look at
this link to that fund on Fido's site, you should see a little red "FEE" tab right under the name of the fund. So the expense ratio is .16% which is good, but they tack on a transaction fee of $75 every time you buy or sell. Not good, and not necessary if you just buy Fido's version(s) of their in house funds which will carry no transaction fees.
Metropolitan West Total Return Bond (MWTRX) isn't that good, and has a 12-1b fee which is crap (it's a marketing cost they kick over to the stock holders - so you're paying for them to wine and dine and advertise their stupid stock). Dump it ASAP. At least it won't cost a transaction fee to get out of it. ;)
Fidelity has virtual clones of all of Vanguard's index funds that are free to invest in (other than the very low expense ratios that all funds are charged). If you had the account with Vanguard, it would make sense to hold Vanguard funds, but you have it with Fido, so sell that Vanguard and trade it in for Fido funds.
IMPORTANT NOTE: Have you discussed rolling the Roth 401k into a rollover Roth IRA ? I don't mean a traditional IRA or lumping into the new company's traditional 401k, this would need to be a Roth IRA for sure. You might need to investigate doing this if you haven't already. It shouldn't cost you anything but they'll have to create a new account for a direct rollover (a brand new Roth IRA for your husband since the 401k Roth is in his name if he does not already have an existing Roth IRA he can roll that Roth 401k into) and it will no longer be classified as a 401k - the greatest advantage is that you are no longer restricted to the old 401k's selections for funds - you can buy any funds you'd like, so that would simplify your investment selections going forward for this. But if he has to establish a new Roth IRA, you will have to restart the clock on the Roth to meet the five-year rule for qualified distributions. But I wouldn't think is a big concern as you're not looking at taking any qualified distributions in the next 5 years. Otherwise, I'd get on that as soon as things make sense to do so.
My suggestion is to do a direct rollover of the old Roth 401k to a Roth IRA, then sell off the old stuff (which will incur the $75 fee to sell off the VTIVX), and invest in a combo of:
Fidelity Total Stock Market Index Fund (FSTVX)
FIDELITY U.S. BOND INDEX (FSITX)
In whatever ratio fits your asset allocation. If you don't want any bonds, then super, but just know that bonds will smooth out the ride a bit when things get bumpy, so if you start watching your accounts every day/week/month, it could be disturbing to see it jumping around sometimes.
You could add if you wanted an international stock (I don't have any because I agree with those that say that most U.S. countries are already pretty international, but there are some good ones if you eventually want to add them in).
Many folks will tell you to get over to Vanguard if possible with the old Roth; I actually like Fido and have all my accounts with them by choice (I have no work ties any more). They have great customer service, great, low cost funds and they are very invested in keeping up with Vanguard so I see no downside whatsoever to staying with Fidelity. And there are plenty of others that feel the same. Vanguard is awesome but Fidelity is pretty great too, so don't feel the least bit worried about staying with them.
https://www.bogleheads.org/wiki/Fidelity^Bogleheads guide to comparing Vanguard funds to Fido
I would suggest before making all these decisions, you do some more research on how the market works, and figure out what asset allocation and your investment policy statement should look like. It will make all of this much easier to figure out. :)
http://jlcollinsnh.com/stock-series/^either read his book (check if your library might have!) or read on the website
https://www.bogleheads.org/wiki/Investment_policy_statement^investment policy statement is your blueprint for how you invest
https://www.bogleheads.org/wiki/Asset_allocationVery important to figure out so you know how much of what you want to hold
https://www.bogleheads.org/wiki/Lazy_portfolios^great examples of "lazy" portfolios - non complicated and easy index investing
Good luck and do not be afraid of asking for help here - there are some really wonderfully smart and kind folks here that can help out with just about anything you could think of investing-wise.
And have to say, do not let this stuff intimidate you; I knew NOTHING about investing about 3 years ago. The Collins stock series I linked to and many amazing folks here gave me a crash course education and I'm doing fantastic now. If I could figure this out, anyone can. :)