I'm looking at getting some more camera gear for my birthday/mother's day gifts to myself

I probably need to keep it under $600 or my DH will be mad..
Here are the things I've been looking at..
Canon Wireless Remote Control RC1 for Digital Rebel
22.25
Canon Speedlite 580EX II Flash for Canon EOS Digital SLR Cameras
406.17
Lenses
Canon EF-S 18-55mm f/3.5-5.6 IS SLR Lens
175.95
Sigma 28-70mm f/2.8-4.0 High Speed Zoom Lens for Canon SLR Cameras
79.95
Tamron Autofocus 28-75mm f2.8 XR Di LD Aspherical (IF) for Canon SLR Cameras
357.85
Will any of these lenses work good for shooting "snaps" inside my dark house and also outside in full summer sun?
Will any of these work for my "studio" type photos with natural light (I usually use f/2-3 with my 50mm 1.8).
I don't really know how a speedlite works, but I know I need help taking pictures indoors.. can I also use the speedlite for my "studio" photos?
What's the difference between the 430 and 580 speedlites? Will my needs be met with a 430 instead of the more expensive 580? I'm mostly taking pics of DD and doing free photoshoots for friends/family, word of mouth is spreading fast though and I get inquiries from strangers pretty often now. I hope to someday make a career out of photography.)
I'd like to cut costs, but I don't want to need to upgrade down the road and lose money overall..
I haven't touched my camera in a month, so I am really excited to get my (only) lens back from repair and get practicing again! Being without my camera this long definitely makes me see the need in a backup lens or 2 asap!
Thanks for any input you can give me!!