The ~ (tilde) should not be attached to your nickname, it should be on your IdentD (nick!
~identd@hostname). This means that IdentD is not installed properly. You need to use port 113 and type
/identd on.
Further suggestions for enabling IdentD can be found in
this thread.
DCC sends being erratic is a little strange, if one person can connect to you, then they all should be able to - it could be conflicting port usage or even to do with the mIRC version. Try looking at the
Can't DCC Send thread.
Out of interest, why are you sending 100-150 files everyday? Why are you downloading?
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this post may interest you.
Regards,