Reverse sear questions

Finally broke down and got the spider to use to sear steaks. Going to butcher tomorow to get some 1 1/2 -2" ribeyes. I have a couple of questions to help make this go as smoothly as possible since its my first attempt. I've been reading on techniques used etc. as far as putting the ci grate and spider under the plate setter while getting the steaks to 115 internal. Here are my questions (as ridiculous as they may be) I am under the assumption when taking the egg nuclear that I want the temp stabalized at 700? Does this mean to leave the to vent on but completely open, our no vent at all, If no vent at all what is to keep it from going to 900? Also while searing do you close the dome or leave it open?