When I installed morroblivion for the first time I looked on www.uesp.net information about the morrowind quest.
When I saw that the original and supposed behaviour on the original morrowind doesn't work properly(due a script bug) , I asked on this forum if this was restored in morroblivion v55. The answer was a no. So I tried to implement this into a mod.
What this mod does:
restore the original behaviour(killing the ash vampires now weak dagoth ur)
removed some unused declared variable
removed the "forceav magicka 2000" function (on Gamemode block) on the script attached on dagoth ur.
changed the fatigue value on dagoth ur to prevent negative fatigue numbers that can lead to CTD
Dued the fact that this mod will modify some of original morroblivion script there can be some bug. If you have problem please write it here. However I fully tested it.
Download v1 beta1 (file with the changes shown on third post, however there is no dirty-edit)
http://www.mediafire.com/?yde9ygdwb8nl2to
download v1.1 beta1.1 (clean mod file with only the changes written above)
http://www.mediafire.com/?b30bcr9dj974zdn
Mighty Dagoth Ur Patch(requiredo to be loaded after Mighty Dagoth Ur esp that is required) :
http://www.mediafire.com/?or9ti26eha256z1
Warning this mod is now merged into morroblivion master v56 please deactivate this esp

Can't test this ingame, but
Can't test this ingame, but Dagoth scripts look alright in editor.
Is there a reason you changed fActorStrengthEncumbranceMult and some teleportation scripts?