Alright, I just finished reading through it, and all in all, I really like it! I'll start with the room to grow, and then end on a positive note with the things I really liked.
So for starters, the first thing I noticed about the comic is the font. Comic sans is a really fun font, but I'm not entirely sure it's what you're going for. You might want to check out some other sans fonts closer to the font Marvel uses (called Benton Sans Extra Comp Black according to Google). Another aspect of the typesetting that could be worked on is the boxes and bubbles, and fitting the text inside of it. Occasionally the text seems like there's not enough or too much to fill the space, and they're sometimes positioned in locations that feel "off." You could fix this by doing your bubbles after the text is down, which allows you to size them around it, and then if you have the text and bubbles on their own layer you could use the transformation tool to move them to a compositionally-pleasing spot. To move from typesetting onto visuals, I noticed some panels are rather grainy and low-res. Since I don't know your process, I can't say how this happens, but drawing to full scale or saving small drawings that you want to expand as png files could remedy this. And on the topic of quality, this isn't major, but the re-using of panels gets to be a bit much sometimes. While there's nothing wrong with re-using a panel or two occasionally, if you're going to have a long dialogue sequence, you might want to just go in and change each copied panel a tiny bit, even if it's just the character's mouth, to make it less noticeable to the reader. Lastly, I was slightly confused on an aspect of the worldbuilding: while Frank seems bewildered from just learning that demons exist, it's also established that there are groups in place who exterminate these demons. I would recommend making it apparent if demons existence are common knowledge or some sort of secret.
I hope that wasn't too much negativity to throw at you, because I did really like a lot of aspects of this comic! First of all, as I mentioned, the backgrounds. The panel backgrounds, in the beginning episodes especially, do a great job of establishing the setting and really add a lot to the atmosphere, especially the very brown color scheme that really sells the idea of the wild west. The dialogue also really helps with the atmosphere- the characters speak like where they're supposed to be from, and the accents are well written in. I also really liked the combination of cross-hatching and simple shading, especially in more dramatic scenes that also had a lot of hatching showing some kind of movement. The additional lines set the mood of intensity really well. I also wanted to praise some improvement I noticed from the beginning to the latest chapters- the pages became slightly more compact so the gutters weren't gaping white holes anymore, and the lineart felt much smoother. Both of these changes were really cool to see. And, last but not least, some things I just really liked were Annies hair (the detail in the stray hairs were really cool), the introduction (the writing just hooked me in), the half demon explanation sequence (really interesting visuals) and the demon itself (great job at making a real spooky boy).
Sorry that I just practically wrote you a whole essay, but I hope I wasn't too harsh and I can't wait to see where your comic goes.