have you pulled your plugs yet? if not do that and see if they are wet, that will also tell you that you have fuel to the plugs, also might be a good idea to change the plugs while you are there. Some times fouled or faulty plugs can give you some of your problem, i would pull them check, and probally replace to rule that out.

when you checked for spark did you check at the end of plug wire? i am assuming you did, if you have a bad wire may give you a issue as well. When you pulled the ICM off (havn't looked at the 5.8 myself) did you pulled the dizzy cap? If you did was it clean not corroded? check for cracks, sometimes not even that visible so may be there and you not know it. also any connections(electrical) by the dizzy pull apart and clean them making sure to have good contact.






(i belive i have this correct on the compression, others may chime in)
you said you have some mechanical skills so perhaps you checked this most of that already. oh one more thing i just thought of, if you have a really corroded plug(lots of carbon) spark can jump to the carbon under compression and not ignite your fuel so that is also something to look for.