I wonder if the gas-burner is for paint-stripping.
Item 2 I'd say a sight-glass as well, though not for a steam-engine's boiler. Catering or brewing equipment perhaps. The two lines may be max/min levels but could also be for metering a small quantity of fluid into some other vessesl.
Item 3, hard to make out and I can't establish the scale, but it looks to me like the generator for a small acetylene lamp, still with the calcium oxide residue in the upper part (the part you are holding). It look similar to the "Premier" carbide cap-lamp once used in non-gaseous mines, and until around the 1970s, by cavers: I still have two or three of these.
If so the calcium carbide was placed in the lower section, and water (the reagent) in the upper half. There would be a small valve in the central tube somewhere to give a slow drip-feed of water, perhaps in the reservoir; and the cork (or felt) plug is a filter to keep carbide debris out of the gas outlet leading to the jet. The action is similar to the Kipps [Gas] Generator used in chemistry laboratories
A photograph of it assembled and standing upright next to a rule or scale-object would help, if you can, please.