> 
> Q1: I want to trim down the sources I'm using - I don't intend on
> cross-compiling (on this platform), can I kill off all of the
> /usr/src/sys/arch/* directories (exceping, of course, vax)?
Yes, you can. There is no dependencies on any of the other platforms.

> Q2: I want to use this machine to dial my ISP, who will be routing me a
> 16-ip subnet. How can I use the vax as a gateway? I see the option in
> the configfile, I also see it in rc.conf, but when I do man gated or
> the like, I get nothing. Will routed, if the kernel is compiled with
> option gateway, act as a gateway?
The kernel itself forwards packets if you turn on packet forwarding.
sysctl -w net.inet.ip.forwarding=1
routed or gated is only needed if you intend to play with routing protocols,
which you probably don't need.

> 
> Q4: As the DELQA is a relitively slow ethernet card, I was wondering:
> Does anyone know how fast a DENLI is? I happen to have two DELQA cards
> and a DELNI - I wonder if there is a way to do load-balancing. Of course,
> this isn't going to be much of a factor most of the time.
The DELQA isn't a slow ethernet card; it's the machine that is slow. 
I have gotten 700K/s through the DELQA on a MVIII. The DEQNA is slow,
though. But to your question: no, you cannot do load balancing.

-- Ragge