Fabricate doesn't cause the creature with the ability to enter the battlefield with +1/+1 counters already on it. For example, Weaponcraft Enthusiast will enter the battlefield as a 0/1 creature, then its fabricate ability goes on the stack. Players may take actions (such as casting instants) while the ability is waiting to resolve.

If Marionette Master's power is negative, the target opponent doesn't lose (or gain) life.

Artifact tokens that are sacrificed or destroyed are put into their owner's graveyard before ceasing to exist. If you controlled the token, Marionette Master's last ability will trigger.

If Marionette Master and an artifact you control are put into a graveyard at the same time, Marionette Master's ability triggers.

You choose whether to put +1/+1 counters on the creature or create Servo tokens as the fabricate ability is resolving. No player may take actions between the time you choose and the time that counters are added or tokens are created.

If you can't put +1/+1 counters on the creature for any reason as fabricate resolves (for instance, if it's no longer on the battlefield), you just create Servo tokens.

The amount of life lost is determined as Marionette Master's last ability resolves. If Marionette Master is no longer on the battlefield, use its power as it last existed on the battlefield to determine how much life is lost.