Hi kumangal,
Just to share my opinion.
Had roughly ran through this thread and I have to say I agree with
AEN, maggot and bohiruici that it is really not advisable to rear
KMT or any sort of spirits, especially if they are from lower
realms.
Definitely it can be seen that you have certain kammic affliations
with these spirits. It will be good for both you and the kmt that
you seek a well-learned venerables to advise you in releasing them
and pray for their deliverance.
To my understanding, even in Thailand, there seems to be a few
methods in making a KMT into a bucha. However what methods are not
that important. The essence is that these spirits are sort of
magically bounded to the statue to do the owners' biddnig.
Of course you may not be asking them to do bad things or what now.
But sentient beings are interesting being as our minds are
ever-changing.
One day you may be that badly offended and back home, you see that
you have a spirit to your bidding. Won't you even feel
tempted to take the chance?
Best way is to have them chao du or if you're
saying your spirits is to gain merits, then send to a proper temple
for them to receive the Teachings and offerings there instead of
sheltering it in your house.