You could also lower the crossbar of /f/ (and correspondingly that of /t/, I guess) a bit, rather than raising the ascender.
I think you've observed well the parts that most need work. (Though the /z/ isn't a nightmare - maybe just needs a wider base.) Once you can get a good suitable hook shape, that will largely solve the problems of /f/j/y/ (and /r/ too, and maybe even /s/).
I'd try a /v/ and /w/ that are less flat on the bottom.
Bottom of /t/ looks a little weird to me too.
I find the /x/ very interesting!

Hola Fernando. My considerations:

01: acute inclination was the first thing that did call my attention. It's semi-horizontal and very large. Of course, this is a design choice, but you must take in account three consequences: (a) large acute means large grave, with undesired collision in fì. (b) It demands special kerning to i as the accent is larger than the letter. (c) You need alternate accents to get correct Polish diacritics because kreska, although similar to acute, is almost vertical.

02: c seems a bit narrow to me.

03: g could get two small improvements. Ear may be more thin at the base, where it links to the first bowl. And second bowl could have a subtle angle in its internal curve at left, following in some degree the standard of o.

04: I understand you want to apply the angled cut in all glyphs as this is a distinctive element of Fenix. But sometimes this may need to be softer to avoid a forced appearance. It's the case of j. Right line seems OK, but the left side would have a simple curve or a very subtle angled line.

05: I like your k. Not boring to me. The same about z, quite good.

06: s may work better with terminals reduced a bit.

07: what about an ink trap inside the middle internal angle of w?

08: I'm not the one to talk about y terminal or f ascender as these were problems to my own font...

Your tilde is very nice, but the dieresis needs dots a bit more near. Excellent p, q and x. General design is beautiful, with a lot of character. I think this will develop to a very good result, as you already done with Quiroga.

@eliason

Thanks for the comments, I'll try them on my new version.
The "v" and "w" looked wierd to me, but I didn't know why! now i know :)
PS: .I preffer not to lower the crossbars becouse they are alligned to the "x" height, but, I'll give it a try! You never know, right?

@Freiberger

Thanks for commenting, I agree with your comments, really helped!
Later today I'll be commenting on your work :)
Quiroga was my first font! This is my second (along with libertad, and I'm working on a script called "Helena" too).

I'm liking this one, it's lovely. It'll be interesting to see how you resolve j and y. (But probably a good idea to sketch out the uppercase first). Unfortunately I'm not able to look in depth right now but hope to come back to you in a couple of weeks with some crit.