Wa alaikum assalam.
I think there are two separate questions in your email.
Lobsters and crabs are fundamentally
sea animals or more technically,
marine crustaceans. Therefore, in my humble view they would fall under the
'catch of the sea' and thus permissible to eat from a Quran’s perspective. Please see verse 5:96 and references
[1] and
[2] below.
However, your question about the most appropriate method to kill the creature is a separate one. We can discuss the most appropriate manner to kill the creature but that should have little bearing as to the fundamental permissibility of whether a creature is allowed to be eaten or not from a Quran’s perspective.
There are discussions as to why lobsters are killed in a certain way and whether or not it feels pain in the manner we understand it. Such a matter is always open to discussion to improve thought and practice.
I hope that helps, iA
Joseph.
REFERENCES: [1] Are Prawns / Scampi's Halal to eat?
http://quransmessage.com/forum/index.php?topic=100.0[2] FOOD PERMISSIBILITY AND PROHIBITIONS
http://quransmessage.com/articles/food%20restrictions%20FM3.htm