Gday Heathen, The It was the Millerites who got th edate of 1844 and they expected christ to come to earth to take the church home to heaven. The SDAs then reinterpreted the date of 1844 to be the pre advent judgement. The date is caculated from the verse in daniel 8.14. 2300 days at the same start date of daniel 9 and useing the day year principle brings it to 1844.
There is no doctrine of the invisible presence in fact the SDAs see the second coming as visivble when every eye will see him. Also the purpose of the second coming is to take the faithfull to heaven. Therfore the second coming is still in the future.
The doctrine of the investigative judgement is now a contraversial doctrine with more traditional Adventists still beleiving it while scholars and the younger generation and those who are clear on the gospel oppose it.