After the scroll was found on the dead body of the orc mage in the lair of Tim the Moonslayer, Maldoor eventually cast read magic and that was how we knew it was a scroll of simulacrum?
Yes.
Casting read magic would have set off the explosive runes?
Yes.
Therefore the explosive runes must have been added after it came into our possession?
That seems like a reasonable assumption.
The scroll was in Maldoor's possession the whole time?
I doubt he had it on his person the whole time, but it certainly has been among his possessions ever since it was discovered.
Since Maldoor was uncharmed sometime before we set off for the Nameless City, he would have remembered if Philomena had put a spell on the scroll — and didn't they only communicate by letter afterward anyway?
I've been ruling that charm person doesn't obscure your memory for things you did while charmed, and Maldoor does not remember Philomena taking particular interest in the scroll and did not observe her do anything with it. Yes, subsequent communication between Philomena and Maldoor has been by letter only.
The blast from the explosive runes was many, many dice - so the caster must have had many many levels — more than Philomena seems to?
Little is known about explosive runes, as it is not a spell taught as part of the magic-users' canon in this age of creation. (However, to spare you some OD&D scholastic effort, its appearance in Supplement I describes it as doing only 4-24 damage, far less than observed. Damage is not scaled by level, but a M-U two or more levels higher than the caster would have a chance of detecting the runes).
Therefore, Philomena is not responsible?
None of the above facts point strongly to her, other than that she had access to Maldoor's possessions while he slept.
Unless it's possible to use a scroll of explosive runes to safely cast explosive runes on another scroll?
Yes, that is possible.
And the Lich (whose name I forget) was not ridiculously imprudent in using the scroll without more caution?
In retrospect, it certainly does seem that Patoriki Van did not exercise sufficient caution.
10. Other mages we are aware of are Ashur Ram, the 4th Menegril, Tri-Kwang, the 9th Menegril, and the Dog Brothers, none of whom had access to the scroll as far as we know?
Not as far as you know.
John Fighter rides out to the caverns and asks Ontussa the Sphinx, "Who put explosive runes on the scroll of simulacrum?"
Do you want to heal first?
With our good relations with the dwarves of Drum Coggo, can we arrange an exchange of platinum components for gold?
Yes, I will assume that a mission to sell the platinum components sets out for Drum Coggo eventually. Does anyone want to take some or all of their share in semi-intact components rather than coins, gems, etc.?
What is our general knowledge of the time frame in which a lich regenerates his destroyed body?
Liches are not mentioned in any of the canonical texts on the undead, and phylacteries are discussed in some of the speculative tomes and rumors you may find (i.e. the AD&D Monster Manual) but not others (i.e. OD&D Supplement I). Neither mentions the ability of the lich to regenerate if the phylactery is not destroyed.
John also asks Ontussa, "Where is the lich's phylactery?" and, "What does it look like?"
We'll answer those once your ride takes place (I'm assuming you'll spend at least one night regaining hit points at the Stronghold of First Principles before setting out).
Does anyone else want to pose questions to Ontussa the Sphinx, who provides answers for 100 gp each? Her information has so far always proven reliable, although her answers are not always as in-depth as might be wished.