About first question, 64 Bit Client will only be installed on 64 Bit Operating system and same ways 32 bit goes only for 32 Bit. So that means if it got installed fine on 64 Bit machine that means it is installed as 64 Bit COmputer.
Seconds question, You see successfyl because the package was actually sent to the clietn computer but due to some problme on the remote machine it didn't got installed
As you said Windows Installer service was disabed(not enabled), try enabling that and install it again.
To further find the reason why it didn;t got installed, do the following
Start -- Run -- %temp%
Look for SEP_INST.log file and look for "Return Value 3", Check few lines above this line and you may be able to find the reason.
You can also upload the logs here, me or someone will look into that and guide you further