Sarnov's food supposedly contained rat poison to "3 times the level of human toxicity". In reality, the poisonous dose (not level) not just depends on the poison but also on the size of the subject - an amount barely sufficient for a mouse will not harm a grown man. Seeing that the poison was sprinkled onto his scrambled eggs, there simply is no way at this stage to tell just how much poison he ingested before stopping to eat at the onset of symptoms.
In the Russian language, last names have a feminine and masculine intonation. Calling Eric's father Alexander "Sharova" would have been a very serious offense because that is in fact the feminine version of the name. His real last name would have been "Sharov". "Sharova" would have only been used in case there was a wife, mother, or sister present. Also if Eric was to have taken his father's full name, he would have been either "Eric Alexandervich Sharov" or "Eric Alexandervich Delkotrovsky"; depending on which the writers were using. The father's first name is always used as a surname in both male and female cases.
In Season 1 or 2, Tim Speedle asks Eric Delko what his last name stands for. Eric replies that "Delko is short for Delkotrovsky." He then proceeds to tell Speed that his father was Russian and his mother Cuban. Now in this episode it is revealed that his father's last name is all of a sudden "Sharova." It doesn't make any sense why they would use this random name when there was already a full explanation given in the beginning many seasons ago.