Is this a suitable arena for The Destroyer?

I'm trying to get an arena ready for a big fight against The Destroyer. I built this arena above The Dungeon after defeating Skeletron. After a long time on the wiki, my friends helped me figure out a good arena. But while I'm building this, I have doubt that this is a good arena.

Should I stick with this arena and continue what I started, or should I completely restart and change to something else?

You got the right idea. However it's too short. You need at least triple that length. Preferably 4 or 5 times. The Destroyer is really long and you will run out of space quickly.

In addition each platform is a bit too close. Unless you don't have rocket boots they will slow you down instead of helping.

Finally you could use some heart lanterns and campfires to aid with health regen.