Thank you everyone who helped me with tips and advices. I tried Genesis Viewer and it really looks like a good viewer. The only issue I had was visual only (I wanted the toolbar buttons as icons instead of names and edit their position of them at my screen). Even so, I crashed few minutes later using it, and realized maybe the problem was different than I thought. So, in the end, coincidentally there was a power outage on the day that firestorm updated, and this damaged the computer's power supply, making me believe that the problem was in the new version. By changing the computer's power supply, all problems were resolved. Now I'm back in Firestorm and so happy to escape this nightmare. Frankly, I love the tools that Firestorm has and I'm really used to the viewer after using it for so many years.
Thanks again and I hope this thread helps other players who have similar issues in the future.
Kisses (◕ᴗ◕✿)