In the ocidental music Db = C#. I invite you to play a Db and a C# in a guitar or Piano and show me the difference.

You can even name your C as Dbb, if you like (or if your intent is to stick with rigorous musical notation conventions, aplicable in some situations) but it doesn't implies in any advantage to someone working with midi notes in a DAW.

It is advantageous to maintain the proper enharmonic spelling due to the implied function, whether or not you are entering a note directly into a sequencer. You WILL think about the note differently if you keep in mind the implied function (and if you don't, you've improperly trained your musical instincts).

And ignore that distinction on the written page, you'll cause unneeded readability problems and confusion, both in terms of function and direction of musical line.

And as for playing a Db and C# on a guitar, the actual note that is played is going to be dependent upon the accidental. If you've ever spoken to a string player, they'll tell you flat out that they treat Db/C# and other situations differently. Typically, for example, if C# and it's ascending, then they are actually going to play the note slightly "sharper" than is possible on the fixed tuning of the piano; for the Db, slightly "flatter", as the emotional pull toward the succeeding note is going to be different in both circumstances. How much of an inflection they use is going to be dependent upon the musical context, style, and whether or not they are playing with other instruments that have a fixed tuning like the piano.

I might also add, someone adding notes in a DAW may wish to keep such a distinction in mind in order to more authentically capture the sound they're looking for.

Gee but that's obnoxious. I could show you how I would inflect a C# differently on a guitar owing to musical meaning, a context, but I don't reckon you'd get much out of the conversation.

Spelling has meaning in functional harmonic practice. C# in an F key has implications of function to someone interested in that. As opposed to Db. For instance a modulation to a D area could follow. You would not use Db to get there, conceptually.

Your mind has not absorbed any of this, apparently. You don't have it. You throw about high-dollar terms you don't know. You wanted C# to mean F harmonic minor as if a modulation; that's out of your ass, now you seek to justify it, more pretending.

It's a matter of understanding. Understanding has its advantages I assure you. I work with the piano roll in all that I do. I know from the explicit advantages of understanding what leads to what conceptually.

I am going to go out on a limb here and say you are actually in A minor. I say this for a couple of reasons. First, it fits all of your harmony except the opening chords of the verse and the bridge. It is not unusual to substitute a major for a minor. Granted, it is more often done on a ii or vi in a major scale, but there is nothing to say it can't be done on a i chord in a minor scale.

Second, I looked briefly at the music you posted, and it seemed like you spent a lot more time in Amin rather than Amaj.

If it is any consolation, I have used that verse progression before. In my case, I added a maj7 to each chord which increased the ambiguity, but I like a bit of ambiguity in music.

what I saw had key sig of A major and I found no problems with that.

here's a tip: if you have a real, full modulation you'll be more or less impelled to a new key sig.
eg., the F naturals I noticed in A major are no problem.

you can mix the 'major and minor modes' and have no change in key. It's been done for centuries. They call it 'borrowing from'.

you can also decide what you have is your own scale, which can be called 'artificial' or 'synthetic'. EG: A B C# D E F G.