Hi everyone,
I'd like to thank all of you for welcoming me and for your replies!
I apologize for not mentioning, in my initial message, that the first thing I did when I started this process was reading all the documentation on the Amiga Explorer website. I followed all the steps to make sure the settings for the serial connection are the same on PC and Amiga.
Although I still remembered something from the past and I just needed to refresh my memory, I found and printed useful guides such as how to use CrossDOS (it was introduced with AmigaOS 3.0 and 3.1, so there's nothing I can do with my primitive 1.3), HDToolBox, and the different ways to transfer files PS<->Amiga. I also found useful notes that I wrote in the past, but unfortunately while those info worked perfectly for my old Amiga 1200, the same cannot be said for this very limited Amiga 500.
For this reason I don't think I will waste money expanding it too much, especially if it's impossible to add an HDD or internal/external CF adapter like I did with my old A1200. My plan is to make it functional enough to enjoy it until the moment I'll be able to resell it (I also have its original box) and finally afford another Amiga 1200. I even kept the internal CF adapter, CF cards, cables, external CD Rom, network card and many other things from my old one.
Matt_H: it may sound silly, but the reason why I uninstalled the latest version of WinUAE and I am now using an older and more stable/complete one is because the possibility to mount external/removable devices in the Settings has been removed (my USB floppy drive, in this case). Moreover, I also noticed bugs in the latest version. For example, the keyboard becomes unresponsive when emulation is on, and many adfs won't load, making the emulator unusable. Until the developers fix those bugs, for the first time ever I will only use an older version.
You're right, utri007. I realize that the null modem cable I have might have become defective during the years. After all, I bought it about 15 years ago for my old A2000 when I was still living in Europe. It could have got damaged when I moved to the US. Also, I opened it and even tho I'm not an expert, I believe it may be improperly wired for this purpose (according to the scheme posted on the Amiga Forever website). I'll post here a couple of photos of the wiring of my cable so you can have a look and eventually let me know what you think about it.
Yes, unfortunately the cable that giZmo350 recommended is for older computers with a serial port. The only solution that works for me is a DB9F/DB25F null modem cable, and a DB9F to USB adapter. That Monoprice cable I purchased after doing some online searches and reading about that in some post should work for Amiga 500, or at least that's what I read in some positive reviews. Keeping my fingers crossed.
I should receive it between November 10-16. If it won't work, I think I'll go ahead and purchase an internal Gotek drive.
Well guys, I'll keep you posted. Thank you again for your help!