Mouse over unit card, you see in the editor, so if you move over a units card you can change the amount of units it has.
For the skill points, you need to open the heros card. then change the value. then close the heros card and reopen it, then you can spent the skillpoints.
The way fast construction works is you enable it, then you build something and that building will finish construction in 1 turn instead of more 2/3 or more turns.
In other Total War games the easy construction option has a time limit that disables itself after a few seconds, maybe thats the same here. did you try activating it again after you see no change or it not working anymore?
I had tried loading the game last night and it didn't work but when I tried this morning it did work, so I'm not sure what went wrong there, very possibly human error. Thanks!