Okay, so I'm going to give you a fill, but what I'm really doing is giving the story of how I filled it, which I hope you will find useful.
First, nothing looks awful. There's potential trouble with the INTH going down next to that E since there'll have to be a vowel after the N, which means that the down next to INTH would have to be ?$v$vE ($v = a vowel) if a vowel went after the T in INTH, so that needs to be a consonant. W might work (TWINKLE and HOWE, for example), but R looks a lot more promising, so I like your R there.
Now what? Well, you wrote IBERIAN, and it's a fine word, so let's go with it. I???A will be tough, especially with an A next to the I (e.g., INDIA crossing NOMINAL would leave me with AA??T, which is hideous). How about IONIA? Perhaps a bit crosswordese, and I don't entirely like IBERIAN crossing IONIA (how much European geography are we going to talk about today?), but let's see. What can I do with the N? I searched and found NAIROBI. I find that word very appealing. It just sounds good to me. Most people know that it's a big city in Africa even if they don't know that it's the capital of Kenya. Doesn't work so well with IBERIAN, but I like NAIROBI more, so NAIROBI is in, and IBERIAN is out.
?B??T is going to be ABORT, EBERT, UBOAT, or UBOLT (don't like it but could live with it). The I in the third letter NAIROBI would be very happy to have an E after it in the down, so let's look for TRE??O? and TRE??E? words. I found TREASON and then caught IMPETUS, which, after some work, gave
I don't like TOSEA very much, and UBOLT is not as good as UBOAT, but it's okay.
I also looked at the TRE??E? words and found TREKKED and TREKKER. That double-K is nifty, and the first K looks good for ARK. How about NOKIA? Oh, look, IMPANEL. The best I could do with the rest was LIRAS and IRA, which is hardly wondrous, but TREKKER is fun. Of course, if you think that TREKKER is dumb, then this line is over, but if not, maybe
I also generally try for the most boring, easy fill that I can get so I have something, then I go back and get more adventurous once I know that it's a feasible fill.
That's how I would work through it. I hope that this helps.