Any recommendations for how I can respectfully delay this initial offer until I have a better feel for these other opportunities? I have great respect for the Hacker News audience and would appreciate any advice.
Feel no shame about reneging on the first offer. This is a dog eat dog business, and the biggest mistake I probably have made in my career so far was not reneging for a better offer. I ended up miserable at a horrible company. Luckily I did reach roughly the same salary level within about 2 years, but that's 2 years of making $40,000 less than I could have.
Also, exploding offers are very rude in my opinion. No one should be pressured into accepting a job before they've been able to evaluate all their options