Function to find text between two tags
You code is extremly hard to read. But I belive this is what you are looking for: 

function FindText(FileName: TFilename; const Delimit1, Delimit2: string): string;
var
  Buffer: TStringList;
  PD1, PD2: Integer;
begin
  Buffer := TStringList.Create;
  try
    Buffer.LoadFromFile(FileName);

    PD1 := Pos(Delimit1, Buffer.Text) + Length(Delimit1);
    PD2 := Pos(Delimit2, Buffer.Text);

    Result := Copy(Buffer.Text, PD1, PD2 - PD1);
  finally
    FreeAndNil(Buffer);
  end;
end;