Problems with tempo in 15/8 time

[Knute Snortum]

Hi everyone.

I am engraving a Scriabin prelude in 15/8 time.  I'm having two problems
both related to the tempo of the piece.  Scriabin used a metronome marking
of a dotted quarter note tied to a quarter note = 69 - 72.  I can use
markup and \rhythm to get the notes, but the two notes are too far apart.
I can use two \note keywords to get the two notes close to each other, but
no tie.  So the first question is how do I get the two notes closer.  I've
attached the LilyPond source and a screenshot of my attempts.

Secondly, what's the best way to get the MIDI to play at the correct
tempo?  I'd like to do something like \tempo 5*8 = 69 but of course that
doesn't work.  Right now I have \tempo 8 = 345, which is 69 times five but
is that the best way to do it?

Thanks as always for your input.

--
Knute Snortum

\version "2.24.2"

tempoMarkupA = 
\markup {
  \large
  "Presto"
  \hspace #0.4
  \teeny
  \rhythm { 4.~ 4 }
  \small 
  \normal-text
  "= 69-72"
}

tempoMarkupB = 
\markup {
  \large
  "Presto"
  \hspace #0.4
  \translate #'(0 . 0.4)
  \teeny { 
    \note { 4. } #UP
    \note { 4 } #UP
  } 
  \small 
  \normal-text
  "= 69-72"
}

{
  \tempo \tempoMarkupA
  c'1
}

{
  \tempo \tempoMarkupB
  c'1
}