I'll take a stab at your questions since I'm just sitting and chillin' recovering from a root canal this afternoon, what fun...
1. Regarding buying low, the new money coming in via your contributions will simply average out over time. Some will go in when the market is in sell-off mode and therefore "low", while some will go in near tops. Nothing to worry about since as your account grows the contributions become relatively smaller and smaller. I think on this site people would be referring more to making interfund transfers as close as possible near lows if they are getting back into stocks, thus "buying low".
2. I've always used Yahoo and Stockcharts.com mostly. I'm rather upset at Yahoo though since they apparently have dropped their basic charts feature that allowed putting multiple charts on the same page. For many years I used that and had as many as 20 or 30 5-day charts on the same page, and those are very useful for timing stock trades by attempting to time bottoms...for longer term I like stockcharts but have never subscribed to get all their features. Here's a basic chart of the S fund for example, and you can see that it just bounced off the 200 day simple moving average, a common good place to buy and I think that yesterday was indeed a major low and the place to buy:
$EMW - SharpCharts Workbench - StockCharts.com
3. Friday is a jobs report day if that's what you're referring to, and in general the market usually does well on those days each month statistically. And since IMO the market is now moving into a wave 3 of wave 3 up, the middle of a big move up in Elliott wave terms, Friday should be a pretty good day and it won't end there...just my opinion.