Enigmatic Variations No. 1470 – Level Crossing by Hedge-Sparrow

“Two unclued entries, to be completed by solvers, are the site of a LEVEL CROSSING and an (incomplete) inscription commemorating it. Seven answers require a non-standard method of entry (numbers in brackets after clues refer to entry lengths). The missing part of the inscription is represented by modifications applied to six other answers prior to entry (three each of two types). Chambers Dictionary (2016) is recommended; 40 and 1 down are in Collins.”

The LEVEL CROSSING is HARVARD BRIDGE, which, in 1958, was measured by members of the Lambda Chi Alpha fraternity at MIT by using that year’s shortest pledge, Oliver Smoot?—?nominally, 5 feet 7 inches (1.70 m) tall?—?as a measuring stick.

The ‘inscription’, originally added after this excess of high jinks, reads “364.4 SMOOTS ± 1 EAR” (‘EAR was originally spelt with an epsilon to further indicate possible error in the measurement).

The seven answers requiring a non-standard method of entry use various figures (‘3’, ‘.’, and so on) in place of their textual equivalents (‘THREE’, ‘POINT’, etc.).

The missing part of the inscription (EAR) is represented by three additions and three removals of the word ‘EAR’.

Notation
(xxx) = definition
[xxx] = (anagram/homophone/container/etc.) indicator
XXX* = anagram
< = reversal
REAROSE = removal of EAR
EARBUDS = addition of EAR

Please post a comment if the explanations are not clear.