I am so very sorry for your loss and will hold you in my prayers. I, too, lost my mother just before Christmas from sepsis that developed after surgery, and there was a lawsuit that was settled out of court, without an admission of liability, as is the outcome of most such suits.
Regarding "perforation of stomach or intestine": as a general rule perforation of either would be unlikely in the course of inserting a PEG tube, and if that is what occurred then malpractice or negligence may have occurred. One has to make an incision into the stomach wall to insert the PEG tube into the stomach, and it may be that the doctor cut too far into the stomach (e.g. perforated the far side of the stomach from where the PEG was inserted), nicked an artery without realizing it, or otherwise had an accident as part of the procedure. Whether it is negligence or malpractice will depend on factors such as: 1) did the doctor assess for and recognize the problem, and 2) did he respond appropriately (according to generally accepted standards of practice) to treat the problem and prevent your mother's death (if possible; not all deaths from complications can be prevented, e.g. persons whose general health is very poor to begin with may die from minor complications that most others would survive).
A perforation of the intestine would be very serious as the intestine contains fecal material and high levels of bacteria. If the intestine is perforated the fecal material and bacteria leak into the abdomen and can cause potentially fatal peritonitis (infection of the abdomen, essentially). This is a true medical emergency, and a person with an intestinal perforation should not have been sent home. It concerns me that your mother was sent home rather than held for observation, esp. if the doctor thought something may have gone wrong during the procedure.
I do not know if you were told of the perforation at the time of the PEG insertion or not until after her death. If the doctor thought there was a problem at the time and still sent your mother home, that is concerning. The safest course of action would be to obtain the opinion of a second attorney. Unless the attorney himself is a medical expert, he should have a medical expert review all pertinent records, from those related to the PEG tube procedure to any autopsy that may have been done. There may be a charge to do this, for the expert's time, the copies of the records, etc. I wonder if your first attorney really looked thoroughly at all the records, or if he went more on your reports or the reports of the doctor who did the procedure. If would seem unlikely that he could have done a thorough case review given how little time has passed since your mother's death.
What happened, when it happened, whether it is a reasonable possible complication (i.e. one that can occur even when the doctor is performing at his best and according to standards of practice, which in essence means "the way doctors are expected to practice, the state of the art") or was something that likely would not have occurred unless the doctor did something wrong (was not performing according to usual standards of practice, following expected procedures, taking reasonable care, etc), whether the doctor properly checked for any signs of complications, what he did if any signs of complications were present (was it what he should have done, was it done in a timely and thorough manner, etc) all factor in to decisions about whether or not negligence or malpractice may have occurred.
Dealing with such issues while in the midst of grief is very difficult. It does not have to be handled right away--it can usually be delayed, unless the deadline for liability suits is nearing. In our case my dad pursued the lawsuit, believing that he had to do it for my mother, and it took about two years to run its course. One has to consider whether the circumstances of the loved one's illness and death, the expense, and the likelihood of success are such that a lawsuit should be pursued, and that may not be an easy decision, esp. at an already difficult time. It gets even more complicated, as settlements treat the lost loved one as an asset, like a car that someone wrecked. For example, the loss of an elderly person who did not work may result in a smaller settlement because that person would not have lived much longer regardless, and the premature death did not result in the loss of wages. I remember in my mother's case the discussion of her being a housewife, of the impact her loss had on the family (not emotionally, but as loss of companionship) and a dollar figure being determined based on these variables. It was very difficult to go through emotionally. In the end the settlement was for what to us was a significant amount of money, though probably less so to attorney used to the big settlements we read about in the papers (and far less than any family would think its mother was "worth" in an economic sense).
I have been where you are, and wish you well. Please take care of yourself also at this difficult time, and good luck in whatever action you decide to take next.