What were then the alternatives before the, premeditatedly (respectively) and inadvertently, keyless couple?

To enter or not to enter. To knock or not to knock.

Bloom’s decision?

A stratagem. Resting his feet on the dwarf wall, he climbed over the area railings, compressed his hat on his head, grasped two points at the lower union of rails and stiles, lowered his body gradually by its length of five feet nine inches and a half to within two feet ten inches of the area pavement and allowed his body to move freely in space by separating himself from the railings and crouching in preparation for the impact of the fall.

Did he fall?

By his body’s known weight of eleven stone and four pounds in avoirdupois measure, as certified by the graduated machine for periodical selfweighing in the premises of Francis Froedman, pharmaceutical chemist of 19 Frederick street, north, on the last feast of the Ascension, to wit, the twelfth day of May of the bissextile year one thousand nine hundred and four of the christian era (jewish era five thousand six hundred and sixtyfour, mohammadan era one thousand three hundred and twentytwo), golden number 5, epact 13, solar cycle 9, dominical letters C B, Roman indiction 2, Julian period 6617, MCMIV.

Did he rise uninjured by concussion?

Regaining new stable equilibrium he rose uninjured though concussed by the impact, raised the latch of the area door by the exertion of force at its freely moving flange and by leverage of the first kind applied at its fulcrum, gained retarded access to the kitchen through the subadjacent scullery, ignited a lucifer match by friction, set free inflammable coal gas by turning on the ventcock, lit a high flame which, by regulating, he reduced to quiescent candescence and lit finally a portable candle.

What discrete succession of images did Stephen meanwhile perceive?

Reclined against the area railings he perceived through the transparent kitchen panes a man regulating a gasflame of 14 CP, a man lighting a candle of 1 CP, a man removing in turn each of his two boots, a man leaving the kitchen holding a candle.