What is the startup flag command that makes pd compute audio? I have looked around but can't find the answer.

have you looked at "pd --help"? Oh, that doesn't have the answer. It's actually a little more convoluted than I thought it woud be!

pd -send "pd dsp 1;"

I entered -send "pd dsp 1;" into the message thing but it got the error:

pd: unknown message -send "pd dsp 1
error: ": no such object

Then I tried entering -send "pd dsp 1;" into the startup flag field and I got the error:

error: "pd: no such object

Did I do something wrong?

Also, for some reason, I can't open startup now...

are you running linux? that's a shell command up there.

you could put this in your patch, regardless of OS:

[loadbang]
|
[;
pd dsp 1;(

and yeah, that's a message box that begins with colon return. That will start dsp as soon as you load.