Some running questions

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After the thread on shinsplints (which I have had for years and had some advice) I decided to make this post about a few small problems I have with running.

A little background I have been running routinely for about 6 years. I try to run at least 6 miles a week and try to do 9-12. The majority of this is on a treadmill after lifting however weekends and if it's nice I try to get outside. The only races (which usually just consist of me timing myself) I have ever run where 5K's, with my best time being mid 19 minutes but recently around 23 minutes. Here are my issues.

1)Running on a treadmill- How accurate can do you think the readings are on here. Mainly the speed and distance. It takes me almost 28 minutes to run 3.2 Miles (5K). It seems like Im running way harder than when Im outside, but my time is significantly slower. Also, I don't really understand how the calorie counter can be accurate.Sure, I enter my weight but wouldn't height,stride,heartrate ETC ETC have some play in this also?

This next question is serious I'm sorry if it offends anyone

2) While running my balls really bother me- I wear boxers and it seems like they always somehow rub between my legs in An annoying way. When Im outside I can usually keep adjusting but it's hard to due in a packed gym. I have tried boxer briefs and it's still uncomfortable. Should I switch to tighty whities? Is there some special technique I don't know about?

3)The best way to decrease my run time- I want to be able to run 5k's in under 18 minutes. My friends have told me that HIIT is the best, but I really hate doing sprints and stuff like that.

Pretty soon I would like to start running 10k's and long term I want to complete at least 1 marathon.

Thanks for any help!