Did an amputee, invalided out of the French army, get a pension in 1916, and if so, how much in francs per year?
I don't find any figures for the year 1916. It appears to have taken a few years for the pension program for WW1 veterans to get established. Discussion of this can be found in the book on The French Army and the First World War, by Elizabeth Greenhalgh. Discussions began in 1919, and by 1922
1,117,874 disability pensions were being paid to ex-servicemen.
Concerning the amount paid:
The pension law promulgated on 31 march 1919 awarded 2500 francs to a private with 100 percent disability, plus 300 francs for each dependent child and 400 francs for each elderly dependent; widows received 800 francs. Medical care was provided free of charge.
This figure seems to comparable to an average yearly salary at the time.
By way of comparison, a woman typist might earn 1,800 francs a year, rising to 3,600 by the end of her career; a miner in 1919 earned over 3000 francs.