Some noob questions...

[Havan_IronOak]

I tried to find a search facility for these boards but no joy.
I also tried to use Google, still no joy
So, I'm posting the questions here. If anyone could help or point me to the right way to find the straight dope, Thanks in advance.

1. How does one MODIFY a chart Mark?
(the little x' made by the marker (pencil) The Manual (PDF) says that the pencil can be used to make or MODIFY marks on the chart. It mentions that the default names are mark 1, mark 2, etc. Also there is a 17 character limit. But it doesn't say HOW to modify the text of the mark.

I'm guessing that this IS possible because when I accidentally leaned against my keyboard while marking new sightings one came up with a string of garbage rather than the usual mark ## label.

2. Is there any way to erase all chart markings at once? I make a lot but like to have a clean map at the start of a new mission.

I'm sure I'll have more question but I'll post these two now and see if I can get any guidance before typing up the rest... Or I'll post them as replies to this topic.

3. How do I decide if a given reported spotting is close enough to be worth chasing? / What do the various speed term MEAN (in terms of numbers)?
I've looked everywhere I can think of and not been able to find a tutorial for efficiently determining if an intercept course is possible given semi-distant position, course and speed reports. Obviously some are obvious but how do I make the closer calls? Part of the problem is that I can find nowhere that actual values are given for the speed terms, slow, medium, fast, and very fast. Can somebody tell me?

4. I found what I believe is a bug in that my CO2 levels sometimes fail to reset when I surface. I find if I save and then reload the save all is well but is this something that is well known? Has it been reported? Where should I report it?

5. Not sure what all is even possible in MODS but I'm assuming that making the difficulty settings related to torpedo targeting more granular is NOT possible. Is there someplace to suggest such a thing? i.e. I think that auto-targeting of torpedoes is a bit easy, I'd love to be required to identify the ship type but am NOT ready for the full on calculations. Getting reliable readings as to ship speed and range from the sonar-man would also be great if they were separately electable.