Usually you can run your startup-sequence by typing "exexute
startup-sequence" but as far as I know there is no way of running it
step by step. For that you will have to open a new shell
window "newshell" then type "ed s/startup-sequence" to display your
startup sequence. Now you'll have to re-type your startup sequence
line by line in the other shell window..
Things might be a bit cramped but as you've got 3.9 and presumably the
latest boing bag you should be able to select high res from the
display options in the early startup menu first.