What IP for network printer ?

Anomalies persist in a new Brother DFC 540CN
printer attached as a network device to upstairs
PC (itself networked by wireless to downstairs PC
which provides both with (wireless) WWW access.)

A. Users of this NG told me I needed a cross-
over Ethernet cable (not straight through as
in Brother documentation.) This worked OK
for test print (text).
B1. Brother BRAdmin diagnostics now report
print function OK but scanner function unready.
B2. I can print text (OK) from Wordpad but not
colour graphics (from Photoshop.) Unexpectedly,
when graphic printing failed there was no report of
this failure, i.e. no / Printer / Properties buffer
reported printing error (and no buffer was saved for
future printing, as happened earlier when text test
print failed.)

IP addresses for all these devices might be set
wrong. I set two of these manually (months ago):

#1 Downstairs PC (with router, hub of the home
network) was set manually at IP = 192.168.1.101

#2 Upstairs Belkin Wireless G card was set manually
at IP = 192.168.1.102
These IPs seem to work OK i.e. successfully connect
upstairs and downstairs PC in my home network.

#3 is the upstairs Ethernet card, into which the
Brother printer is connected. This generated
APIPA = 169.254.136.169

#4 is the printer, which reports
APIPA = 169.254.11.192

MAIN QUESTION: should I manually reassign all these IPs
into the same family, the same as my home network,
and would this solve problems B and C above?
I thought of making them simply
#3 (upstairs LAN card) = 192.168.1.103
#4 (printer on LAN card) = 192.168.1.104
This notionally puts all four devices into a single network.
But do I need two networks (one linking the two home
PCs, the other linking printer to upstairs PC) ?

(Supplementary Q: I do not see why APIPA for the
two upstairs devices were in different "families" i.e.
APIPA = 169.254.136.169
and
APIPA = 169.254.11.192
Should they not be both the same?
Will it disable either to reset them into home
network IPs of family 192.168.1.xxx ? )

(Supplementary Q2: Belarc software reports IPs like
Auto IP Address: 192.168.1.102 / 24
What does the / 24 mean at the end of the line? Does
it mean there is logical room for 24 more devices
in IP family 192.168.1.xxx ? )

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)