Dividing ties and adjusting ties in an arpeggiated chord

[bruys .]

I'd like some help on how to adjust ties. The following example comes
from Behind Bars: The Definitive Guide to Music Notation by Elaine
Gould, p.133; or it would do, if I could get it to work.

The problem is that in this example, there is a collision with the
tie, second from the top (d'') and the f# (fis''). Ms. Gould's
solution is to "divide" the tie leaving a gap in the tie, so that it
doesn't collide. How does one divide a tie with Lilypond?

(By the way, I have been able encode a suggested alternative of using
"laissez vibrer" ties, although I don't think it looks as good.)

I would also like to know how to adjust the curve of ties in such a
situation. In the Lilypond manual, 5.5.4, Modifying Shapes, it states
that "it is not possible to modify the shapes of ties or slurs by
changing the control-points property if there are more than one at the
same musical moment". The same tie intersects the top staff line. One
would like to make the curve shallower to avoid this. One would also
like a shallower curve for the uppermost tie, so the beam on the grace
notes didn't have to be raised as much.

(The tie on the g# also seems to be too short, but I imagine this
could be changed by introducing some padding between the grace notes
and the chord.)

\version "2.12.3"

arpeggiatedchord = {
  \set tieWaitForNote = ##t % as notes intervene before the ties end
  \once \override Beam #'positions = #'(5.0 . 5.0) % raise beam to avoid
                                                   % collision with top tie
  \grace {
    d''16[~ fis''16~ b'16^~ d'16_~ gis'16]~
  }
  \once \override Stem #'length = #'6.0 % lengthen stem to match height of
                                        % grace notes - this seems to require
                                        % 6.0 instead of 5.0, which isn't clear
                                        % in the manual
  <d'' fis'' b' d' gis'>4
}

\score {
   \arpeggiatedchord
}