It definitely is not mentioned anywhere that John and Patsy were overly concerned about Burke's safety during this time. I definitely understand them not wanting him to be around the house for obvious reasons, but wouldn't they absolutely insist that he be guarded by law enforcement at all times? Yet, he was given to friends of the Ramsey's to be watched over. Assuming from the ransom letter that the perpetrators knew quite a lot about the Ramsey's (from the amount of bonus money John received, the way the ransom note was written in regards to how lenient the kidnappers were... by this I mean how the demands gave the Ramsey's options as to when the money could be obtained by John... would suggest that they knew the Ramsey's). I personally believe Patsy wrote this letter. It is definitely that of a female writer in any case, and I just can't see how a female even if they were accompanied with a male suspect would break into a multi-millionaire's house, stay there for quite a while, use their own stationary inside the house and write this ransom letter, and not have some concerns that maybe somebody inside the home would wake up or an alarm would go off.
The one line in the ransom letter that is beyond ridiculous is where it states: "If we monitor you getting the money early, we might call you early to
arrange an earlier delivery of the money and hence a earlier
delivery pickup of your daughter."
Kidnappers don't negotiate or give wiggle room like this as to when money is picked up or delivered. Their freedom is based on a strict outline under their terms, not how the Ramsey's want it to go.
Here is a pretty good link on the ransom letter that has some interesting analysis after each line and paragraph:
http://www.statementanalysis.com/ramseynote/