General Tablature Help

Hi all,

Just started using MuseScore a few hours ago. I figured out how to get a dual staff with upper treble clef, lower guitar tablature. I also figured out how to enter notes.

I'm still a little shaky on how to enter fret numbers on tablature. Here's what I've figured out so far:

1. It seems like you press "N" to enter tablature frets (just like you do with staff notes).
2. You click on a string, and you get a "0" indicating open string.
3. You can then use the up/down arrow to make the 0 into any number between 0 and 4.
4. When you press up arrow to go beyond "4", the tab becomes a 0 on the next string.

I have four questions:

1. How do I get frets higher than 4? When I use the up arrow to increase the fret, a 5 turns into a 0 on the next string. How do I enter frets higher than 4?
2. I noticed that you still have to worry about note durations in tablature. Is that true? It seems like (at least by default) MuseScore should take care of tablature note duration if it has a corresponding staff score. For example, in my attached screenshot, the staff is simply a bunch of eighths yet the tablature indicates quarters, wholes, eighths, sixteenths.
3. Is there any way to get error checking? The tablature clearly doesn't follow the score in either pitch or rhythm. Is there some option I can use to warn me the tab and staff aren't in sync?
4. In the staff music, there's a funny looking space between the E and F#. What's causing that space?

BTW, MuseScore is very pretty. Does it use MusixTex or LilyPond as a backend?

Much thanks!
Pete