I hope that you are using an amp or have a sound card with an adequate amp built in. If not, break-in techniques are not your major problem.
Most people still break cans in (if they do it intentionally) by simply using them--or at most running sounds through them while they sleep.
KRK KNS 8400
Headphone comfort is a very individual thing. Everyone has a different head size and shape, as well as different sensitivities and levels of sensitivity. We can point you to headphones that are generally considered to be comfortable (see above) and mention others that have garnered complaints for being uncomfortable. However, the only way to know for sure is to wear them yourself for a time equivalent to your longest listening session.
For on the go use, I recommend the NAD VISO HP50, PSB M4U 1, Focal Spirit Pro or Sony MDR 7520. These are listed in order from warm to dead neutral (I call it a tie in that regard between the FS and Sony). These all come in at less that half your max budget. ...
That's a mismatch with $1000 can. You need a much better DAC and very likely an amp (or amp/DAC). The weakest link controls what comes out of your cans. In this case your phones and computer are a very weak link for quality (almost) $1,000 cans. Your music files, depending on the format, may be another weak link in your audio chain.
You've IDed some good cans in the general price range. Deciding which one to select will probably depend on what sound signature you like best. Each of these cans has its own. In this price range you tend to get very good cans, but few that "do it all". About the only great all-rounder I can think of in this range is the DT 880 (250 or 600 Ohms )--and you still have to be OK with a can on the bright side. ...