Ok I managed to redo what I did before and indeed it solves the problem of displaying UTF-8 characters in uxterm. But note that it doesn't solve the typing issues in uxterm and specifically what concerns typing letters with accents like á or ò, it only solves the display problem of UTF characters. So I assume iBus is not being able to get through uxterm, IBus seems to be succeeding everywhere else but in uxterm. So:

Here's a printscreen with UTF-8 encoding off (I used a different Xresources file in ~/Xresources I found somewhere which lets the user see 3 different menus by holding down Ctrl and pressing left mouse button, middle mouse button or right mouse button, the menu with the UTF-8 encoding option comes out when you hold Ctrl+right mouse button):



And here's a printscreen with UTF-8 encoding checked:



At least this one is solved, you just have to set using of UTF-8 encoding by default.

So I believe I also found the solution for making iBus work in uxterm. What I have to do is to quit iBus and then start it again on the terminal with the command:
ibus-daemon --xim &

After that, typing letters with accents like á or é or õ works just fine.
I found the solution here, it's kind of an old iBus issue: https://bugzilla.redhat.com/show_bug.cgi?id=506474

How should I set ibus-daemon to start with that command instead of the one it's using now to start?

partner ppa is enabled by default, the touchpad problem i think could have been taken care of in the mouse & keyboard section

check the help file in the accessories menu