Hi all, Thanks again for all your comments and detailed feedback!
Considering, I think I'll leave the plant as it is and see how it copes. Noted I made some mistakes repotting it so I suppose there's a chance it won't make it. Probably the pot size being the biggest issue, 24" was recommended, the one I'm using measures 13". The small pot size is the reason, by the way, that the plant ended up near the side, the roots were shooting off mainly in one direction. (I'd say the root is about centered although the plant isn't). Regarding the soil type, it doesn't say anywhere on the pack that it is meant for pots, so I suppose it isn't. This is what the pack looks like:
My local gardening centre recommended the use of a screen at the base, as was suggested here, this was the idea with using the pebbles, thinking it would achieve the same. I might be wrong about that, but I hope they won't do any harm.
Anyway, there was a couple of things I could do without repotting the plant. I drilled some holes at the bottom of the pot. The pot was actually easy to drill through being soft clay or terracotta. The largest drill size I had was 9mm so that's what I used. The bottom looks like this (they are a bit here and there)
I've raised the pot using a couple of tiles:
Thinking then, I'll leave it at least for some days, and see how it goes. If it survives perhaps I'll repot it
next season, or if it does poorly I might try some more emergency intervention.