For me, the sound FX is very loud. I do like the birds sound. But then in relation to the volume of this ‘ambient’ birds sound, the sounds of i.e. opening a menu or clicking a button is extremely lound (and as I said not very sexy).
Nah. I wouldn’t get that far. I’m no sound eng but I can easily use some effects that makes a sound much better (understand much more in-line with all other sounds). You know what, if you wish you can pass me on some of these samples and I shall run a few fx and normalization on it. And didn’t I just read that @pryme8 also offered the same, so there you go. Besides, I also have some links for free samples which you could also make use of. Really, I wouldn’t invest any money in this at this point.
Yes, I noticed that. Again, I have some tools that can help with this. And then, you know, you could ask the Community to record some samples as a base. I’m sure some people here would gladly give a minute of their time (and voice) to do that. You just need to make a script to make this process ez.
Of course, again, my opinion only and hope this helps.
Meanwhile, have a great day 
Edit: If you want to have an idea of what I can do with sound (at my very amateur level), it is me who did the final cut, fx and normalization of the audio for the ‘GUI space adventure’ video (based on the audio track for the release of v5). Shh though, it’s a secret 
Now, I’m sure I cannot compete with @Pryme8 expertise, I won’t even try 
, …but I think with little effort I can also help you improve things (in case needed).