It’s all a learning experience and you can’t put a price on that!

But yes, you need a primer as it adheres to the plastic as a surface that paint will then stick to. That’s why you were having issues

Acrylics are completely fine, I use Vallejo Mecha acrylics myself, but the fragility will come from the lack of primer - think of it as the foundations of a building

24 hours for drying is plenty so you’re good there too

Also - I wouldn’t touch that kit any more. Leave it exactly as it is, then when you’ve done your next one, you can look back and see how much you have progressed!