You could take it to a parts store chain like Kragens or PepBoys, they usually have testers. That or you could probably rig some guages and do it yourself.
90 amps is pretty good if it can really do it, but I doub't it, plus you do have a lot of stuff going on. I can't say about that pump since I don't really know what you're talking about, but I'd disconnect it.
I've put non oem alternators in cars before the ones I did weren't too difficult. Some just needed some washers to shim 'em up right, others need a custom nount. I made a custom job just a few months ago, it came out awsome. I also made an AC compressor mount for my truck; Toyota Tercel AC on a Chevy V8.

I love amps myself, butt news flash: I've never seen an amp draw what its rated output is. My last car/amp setup was 700 watts which would require maybe 60 amps or so of draw. The fuse was 30A and never blew.
I'll never forget my very first amp and its lesson in wattage; it was rated at 300W, but came with a 5A fuse!