Zarzycki in an article from 2000 writes an interesting thing, that because of lack of howitzers, the 2nd battery (only!) was given 75mm guns.
As for 75 dal, it wasn't C-inc reserve unit, because it became II/65 Light Arty Rgt of a reserve infantry division.
As for 62dal, in reference 4 there's a mention, that Zarzycki writes about 100 mm howitzers in 62.dal. (and he claims so also in other article). I don't know, who is right.
As for 71 dal, there's no reference given. Zarzycki in an article from 2000 writes about 100 mm howitzers.
"Naval Light Artillery Detachment" is "morski dal" (MDAL) indeed.
Armoured trains were meant for wider tasks, than only providing artillery barrage (it's like a tank vs heavy SP artillery). And they appeared quite useful in 1939 as well (note, that also Germans and Soviets built dozens of new trains during the war). Besides, it wasn't a choice, like: "sell our old armoured trains and buy a modern railway artillery for that money" (who would buy it?). Note, that all artillery wagons existed since 1921, and they needed relatively low expenses to keep and modernize them.
Oh, yes, with a hindsight we can easily say what should have been built in the 1930s. Bigger problem is: what to do with the stuff that we haveYes... I think... Mobilization planing (and military bilding at 30th yars) not only much better...it was must be better..