I'm 22 years old and 1.5 years into my first Startup Job. (and second Dev job)
I feel kind of uncomfortable now and I would like to ask your opinions.
I'll start with the work related description of my situation and later add a bit of my life situation.

I develop as hobby since I can think. I'm pretty engaged and love to do things right. So I quickly found myself in the position of the de-facto lead fullstack Developer.
Although, to be clear, were only a few devs - which are now replaced by not so many other devs. I feel often like the only person able to design and decide and implement in a way that won't kill us later (and I spend half of my time fixing technical debt).

I mostly like what I do , because it's a challenge and I feel needed. I learn new things and I am pretty flexible in work time. (but I also often work till late in the night, sacrificing friendship time)
But there are so many things I would love to do and used to do, but now I have no motivation to develop outside of my job.
I don't really feel that what my company is doing is something I find valuable. (Image rights management)

I earn pretty well - in comparison to what I'm used to: 20€/hour, Brutto 2.800 / month for 32 hours a week. In Berlin. (Minus tax and stuff it's 1.800€). It's more than enough for what I need.
But when I see what others in similar positions earn (~4.000), I feel weird. I got promised a raise since nearly a year now. I don't feel I could demand it. I also got the hint that I could get virtual shares. But nothing happened.

Now what further complicates the situation is that I will go to Portugal in April for at least half a year, for joining a social project I love. My plan used to be that I work from there for a few hours a week - but I'm starting to hesitate as I fear that I will actually work more and it will keep me from fully being there.

So, I kind of feel emotionally attached - I like (some of) the people, I know (or at least believe) that the company will have a big problem without me. (I hold a lot of the knowledge for legacy applications) .
But I also feel like I'm putting too much of myself into the company and it is not really giving me back. And it's also not so much worth it... Or is it?

Should I stick to the company and keep my pretty secure position and be financially supported during my time in Portugal, while possibly sacrificing my time there?
Should I ask for a raise (possibly even retroactively) and then still quit later? (they will probably try to get my 1 month of cancelation period upped to 3).

Also, is this a risk for my "career"?