First of all wrongful death is a general term which refers to a law which allows certain claims brought by the next of kin for a personal injuries suffered by or leading up to the death of a person.
The tie between her death and the elopment is tenuous. The statutory damages for the violation of her patient rights, which in this case is to have someone keep her from walking off the property when she is in a state of dimentia, are not going to be high damages. If the case were different, you might have a higher damage claim, but as it is the other side will be pointing out problems in causation. Your attorney is taking the strategy that if you start too high with the demand, then it may cause a rejection with no counter-offer based on the other side's belief that there are serious issues with your case as far as proving the link between causation and damages.
If he does not want to go to trial, this might be because he has serious concerns regarding the winnability of your case. I cannot second guess his work here, as I don't have access to your entire case to be able to tell you exactly what I think about the lower settlement offer.
My experience has been that a high demand will not necessarily cause them not to eventually make an offer that is within an acceptable range, but it definitely may prolong the litigation. In the end, you are the one who makes the decision regarding the number. If you think a low 6 figure offer is not where you want to start, then tell him you want him to demand more. If he cannot convince you that his plan is better, then you should trust your instincts and ask for more.