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I think I have worked out a DFA that doesn't accept the substring "111," but I don't know how to account for accepting even length strings. Here is what I have so far. Any help would be greatly appreciated!

Hi, thanks so much to everyone who's commented. I've made some updates to my answer, and I think it works now, but I'm still not sure. Here's an updated photo below.

Keep in mind that DFA has a "finite" memory, each state knows something about what you've read so far.
$A$ remembers that so far, you've read $w0$ for some $w in {0,1}^*$ or $epsilon$.
$B$ remembers that so far, you've read $w01$ for some $w in {0,1}^*$ or $1$.

and so on...

Now you can duplicate the states to have the following properties:
$A_{even}$ means that so far you've read $w0$ for some $w in {0,1}^*$ or $epsilon$, and you've read even number of letters.
$A_{odd}$ means that so far you've read $w0$ for some $w in {0,1}^*$, and you've read odd number of letters ($epsilon$ has even number of letters, so it's not included here).
$B_{even}$ remembers that so far, you've read $w01$ for some $w in {0,1}^*$, and you've read even number of letters.
$B_{odd}$ remembers that so far, you've read $w01$ for some $w in {0,1}^*$ or $1$, and you've read odd number of letters.

And so on.

You need to re-define your transition function and and accept states to match with the definition of these new states

Edit: I misread the question as accepting '111' as a substring, so the definition of A,B that i showed are a bit off, but the answer to your question is similar in concept.