Means that the script will never run in-game. It needs to be compiled before it can work (open the script in the CS, hit the Save icon, then save the ESP).
It's not used by anything, so harmless, but could just as well be removed.
A persistent object has been placed in a cell in Tamriel worldspace, but the cell doesn't exist (perhaps because it had an invalid coordinate?) so the item cannot be placed. Looking at placed object 'Goldenrod01' it has a bad y coordinate. All other coordinates on this object are 0 (which can't be right either), so the cleanest way to correct this would be to remove 'Goldenrod01' from the ESP (using TES4Edit).
This one caused me some headaches (until I removed it) because TES4Edit filter kept choking on that REFR. It has bad coordinate data, so almost certainly not needed. Nothing else references it.
Script 'EiAMainQuestScript' tries to do something which doesn't work. What exactly, I don't know. Assuming that variable 20 is the 20th local variable in the script (which it might be, I don't know) then the 20th listed is 'EiAGRSpeechTimer' which a FLOAT variable (which can only be a whole number). The script includes the following: 'set EiAGRSpeechTimer to EiAGRSpeechTimer + .5' which would set this variable to a non-whole number (non-integer) and most likely this breaks it, resulting in the error.
"Unable to find variableID 20 on script 'EiAMainQuestScript' in TESConditionItem Parameter Init for PACK Form 'EiAGGWilliamTravel' (01041E0E)."
AI Package 'EiAGGWilliamTravel' contains a condition which references something from the script mentioned in the previous warning, which is missing. At a guess, I'd say a line was deleted from the script at some point, causing both this and the previous error.
EiAGGWilliamTravel is not used, so it can be removed.