It is heartening to see type designers seeking to match various scripts in one font. We have this problem in almost all Indian languages and it is yet to be solved. I cannot speak for Arabic or any of the other scripts included in the font, since I cannot read, write or speak those languages. They look quite well matched and have an even texture. But the structure of Roman script is quite puzzling as so many styles have been mixed making the composed Roman text look quite bizarre. I am sure, if you can spend more time on it, you may be able to improve upon it.

I'm not sure what kind of comment you are looking for. Your friends were right. It's readable. This is impressive for a 2 days effort. But for another 2 years of effort, you will still be in the realm of 'readability' of your Arabic text... only slightly better!
You might be better off focusing on Roman languages for your font. I personally discourage using Arabic in a Roman font. Roman in Arabic font is more manageable -and more necessary.

the connected Y is wrong in what you have so far. In arabic calligraphy standards, it really shouldn't be pointed. The detached Y is better, I like the end of the tail (although it's not a traditional aproach) it mimiks you roman. However the beginning of that Y, it's a little too thick up there. The bottom curve is beautiful, but the top curve has stroke thickness problems.

the Kaf is absolutely beautiful, again the top right tip isn't traditional but it looks like the roman. Now the Waw is perfect but the following letter the R it's totally off compared to the Waw. The descenders in the Waw and the R should be really the same. there's no reason why the R should be bigger. The R is one of those letter that are Huge in your typeface, the "Dal" on the other hand is slightly tiny, I can understand what happened in the case of the Dal, but the R should match the Waw.
The Nun is beautiful too, I can understand why it's slightly slanted and pointed (to match the Roman) but the middle Y that follows it is just too big again. It is both thicker and taller than the Nun and that makes it look like a hybrid. You might want to make a middle Y or a middle Nun straighter than a Beginning Nun or Beh but the x height should be the same really.

The final Aleph like all the Alephs in your typeface I like it, it is coherent with the roman, however you should be super careful with the stroke thickness in proportion to other letterforms.

There is still a lot more to be said. Overall at this point I can compare it to a roman typeface where some of the letterforms are slab and some are old-style.
Part of your challenge is that you can't speak or read the language but hey Herman Zapf designed a metal typeface for an Egyptian newspaper in the fifties and it was still used until not a long time ago. He didn't speak the language but his design was an influence on some digital Arabic typefaces. It's a very challenging task. I have never learned traditional Arabic calligraphy but if you have questions don't hesitate.
Good luck

Thanks for the comments, I'm already working on a few changes.

I knew that Arabic has less defined vertical heights, so I tried to vary them, I guess I got too carried away with it. It's interesting that most here are finding parallels with the Roman version, when actually most of the Arabic was based off of the Greek version :)

Which of these final yehs do you think works best? Also, when you say the R and waw should be more similar, is that just for the descender part (the curve is the same, just lower and wider) or also for above the base line?

«El futuro es una línea tan fina que apenas nos damos cuenta de pintarla nosotros mismos». (La Luz Oscura, por Javier Guerrero)

Ok, the space after the Nun is slightly too big right now. I will say that number 4 is not bad at all, 1&2 have weird proportions, in 3 the fact that there's that lift from the basline that is making the horizontal stroke thinner is very awkward.
So 4 is good: the tail is nice maybe a tiny bit lower. Now when you want to create your detached Y base it on number 4, cut the attaching area and replace it with the swash that goes all the way up to the x-height.

Speaking of which, I think you should have a descender line an ascender line and an x-height. So descenders like the tails of the R and the Waw should be fairly similar if not exactly the same, kinda like the ascender on a "b" and a "d".

I don't know if I mentioned that before but the two dots should align horizontally, I don't want to restrain your creativity, but really if you get rid of the upper dot on your three dots, that's how your two dots should look.