Been there, done that, got the t-shirt, read the book, saw the movie.
I hunted in Birmingham AL. for about 18 months with not only some of the worst mineralized soil in the country, but we also had veins of natural iron ore that ran throughout 80% of the area.
Not only was my depth severely curtailed, those ghost signals you spoke of were everywhere and especially for me because I hunt on max sense most of the time.
Average depth in dry soil when I hunted was about 2-3 inches, every once in awhile I might see a 4 on the depth numbers but that was rare.
This was the same for most hunters in that area no matter what detector they used.
In wet soil I could get maybe an inch or so deeper, maybe down to 5" from time to time.
None of that mattered to me because I still found plenty of great targets, (including silver and gold), and just about all of them were 3" or less in depth.
A little over a year ago I moved to Kansas with much better soil and now my average depth is way more but guess what, I still hunt on max sense most of the time and I still get plenty of ghost signals at most of my sites.
The reason you have most of those extra signals has more to do with the extreme sensitivity of the F2...
and not as much with any mineralization problems you might have.
Not only will the F2 pick up signals from metal in the ground that is under that coil, it will pick up signals from targets that are outside the diameter of the coil, too, and these type of signals will usually come in as ghosts.
The F2 can pick up huge iron objects that will come in as a high tone dime signal even if that object is up to a foot away from that coil, and if you are near trash like foil, can slaw or tabs that are an inch outside that coil you will get that jumpy signal that will not only jump more than 2 numbers on the screen but will also jump into completely different sections.
When this happens notice the depth bars on the right side of the screen because they are gonna jump up and down, too.
This is how I can tell trash from good targets because good targets will not jump in those VD! numbers more than 2, (if at all), and the depth bars will settle on one and stay there.
What to do...
I had a couple of hundred hours with a bad detector when I started that falsed on 99.9% of my swings and I was forced to listen hard and gained the ability to hear the solid and "real" tones and tell the difference between those and the false ones.
This is something most hunters never had to deal with and I wouldn't wish this frustrating experience on my worst enemy, but that ability to tell the differences in tones is something that I retained and I am thankful for to this day.
Even so, when I got my F2 it still took me awhile to figure out these false tones and I dug plenty of empty holes looking for targets that were never there.
Some of the craters I dug in those early days you can still see from the moon.
Eventually I figured out that no matter how solid those false tones are they are not and do not sound the same as real targets and
never repeat in exactly the same place.
Also, if you hit these iffy targets from different angles the readings could change...a lot, another clue you are either swinging over trash or there is trash in the vicinity.
I can tell you after digging many thousands of targets that most of the time a good signal like a coin or ring will be solid, and not jumpy at all on the numbers and the depth bars.
Nothing is 100% in this hobby, and if you are scanning a good target at the outer end of that scanning field, say 8" in good soil on the 8" coil), you can get a squeaky, iffy, jumpy signal on those, but most targets will not be that deep and with practice you will learn to tell the difference.
Turning down the sense will help in these sites with extreme falsing, and don't worry that much about losing depth.
You will lose only about 1/4 inch in depth for every bar you take away and even on one or two bars you will still get plenty deep enough to find some great targets.
A few weeks ago I was at a site surrounded by electrical wires and I actually turned my sense down to about 2 bars and I was still digging tabs, trash and coins at 5 inches in depth or maybe a little more.
I found the best ring I ever came across that day and it was only 2 inches deep.
Most every great thing I have ever dug has usually been 4" or less in depth so don't worry about that, turn down your sense and that will make it easier for you as you go through this initial learning stage.
Another thing you can do is use that sniper coil if you have one.
If not, I would definitely think about getting one.
Out of all the coils available for the F2 I believe the standard 8" coil, the one that most new users start with, is the most susceptible to EMI and false signals due to trash in the vicinity of that coil.
My 10" seems to be a little calmer, and that sniper coil seems to be the best out of all of them because of the much smaller field that is emitted.
Lately when newbies ask my advice on which coil to start with I have changed my mind and always say use the sniper if you have it because it will be much easier to deal with as you learn the basics.
You still can get some falsing and EMI can still affect it, (I was using that sniper when I found that ring I mentioned above), but there will be way less falsing to deal with and less problems with multiple signals hitting that coil like the larger ones could have.
There are other advantages to using that small coil, too, and unless I am trying to cover large areas that small sniper is the one that stays on my F2 98% of the time, nowadays.
Basically you just have to learn the language of the F2 a little more, and understand what it is really saying to you whether it is solid numbers on the screen or jumpy ones.
All that info can help you make an educated guess once you learn a little more of that language.
Here is a thread that is very long but there are lots of tips in here that will help you if you take the time to read it.
This is everything I learned as I learned it and it has insights from other owners, also.
http://metaldetectingforum.com/showthread.php?t=53930
Here is a video I did one day that is not great quality but might clue you in on how to deal with falsing, jumpy numbers and depth bars in the field.
Just keep swinging and learning...it will all come together for you soon enough.