I found age and gender information for some magazines around that era:

Analog - which original published Dune, but the results were from 1958, and they started serializing Dune in December 1963.

New Worlds - from 1963, although this is a British Magazine

The Magazine of Fantasy and Science Fiction - mid 1960s (I don’t know why the paper I found this in didn’t know the exact year, I only skimmed it and looked at the tables). This is an American magazine (still around, but about to fold due to mismanagement). In the late 1950s it published the short story version of Flowers for Algernon, now out-of-print short stories that were expanded into A Canticle of Leibowitz, and Starship Troopers. It has always been seen as more literary and less technical than Analog.

Galaxy - from 1971, two years after they serialized Dune Messiah in 1969

Ages

Astounding-1958
13-17 …(6.9%)
18-20 .... (7.0)
21-25 … (16.8)
26-30 … (20.1)
31-35 … (19.2)
36-40 … (12.7)
41-45 .... (7.2)
46-50 .... (3.6)
50+ .. (6.5)

New
Worlds-
1963

0-19 … (31.0%)
20-24 … (27.0)
25-30 … (14.0)
31-40 … (14.0)
41-50 .... (8.0)
50+ .. (6.0)

Magazine of Fantasy and Science Fiction -mid‘60s.

0-18 …(23.0%)
18-30 … (30.0)
30-45 … (31.0)
45-60 … (13.0)
60+ … (3.0)

Galaxy-1971 .
0-17 (16-17% approx.)
18-39 .. (66.0+)
40+ (16-17% approx.)

Sex
Survey and Date .......... Male . Female

Astounding-1958 ................. 85-95.00 ........ 15-5.00
New Worlds-1963 (British) .........92.00 ........... 8.00
F&FS-mid-sixties ................. 71.00 .......... 29.00

If you have access to jstor, the whole article is here: https://www.jstor.org/stable/4239132

There’s some information about their jobs, but the Analog specific stuff is scattered through the prose. Here’s one paragraph.
“Campbell’s Survey” is the 1958 survey of Analog readers. The references to Toronto regard a survey of people at the 1973 World Science Fiction Convention (the article has alot of information about this group).

Comparing the educational responses of Campbell’s survey with the results of
the Toronto convention gives evidence of a trend away from purely scientific
studies and at least the surface indication of greater breadth due to multiple
majors. In 1958, 66.1% of Astounding readers had majored in either the physical
or biological sciences. By 1973, only 48.6% of the Toronto convention-goers
had done so. Between 1958 and 1973, the social sciences, including education,
library science and communications, had grown from 19.8% to 30.5%, and in
the fifteen years separating the two surveys, studies in the liberal arts, including
law and journalism, had grown from 12.8% to 24.5%. Within those broad cate-
gories, certain specific groups stand out. The largest single educational major
represented at Toronto was Mathematics, 8.5%, but it was closely followed by
English, 8.2%. There were more historians present, 6.7%, than physicists, 5.3%.
There were only 10 students of electronics in the sample. 3.6%. And even if the
differences between the broad membership of the convention and ing orientation of Astounding’s readers are considered, the drop i studies from 29.5% in 1958 to 6.7% in 1973 is most striking.