Not a frequent Delta flyer.
Tried to search the Delta forum, but could not find an answer.

PAID (no miles or upgrades) to fly KEF-MSP in Premium Select then MSP-HNL in Delta One.
Misconnected in MSP by 4 min so rerouted MSP-LAX in first then LAX-HNL in coach.
Arrived over 7 hrs late.

I have 2 questions:
1. What is an appropriate amount to ask for compensation for the downgraded segments (Delta One to first/coach) and 7 hr delay? A friend who is Diamond Medallion suggested asking for $2000 in travel credit (rt ticket cost $3000), but settling for $1500. With anger and emotion (most of the Delta people I asked for help were nice, but useless and one lady at the LAX Sky Club was offensive) I think $2000 is fair, but my rational side thinks I should request $1000.
2. What is the most successful way to request compensation w/ Delta? Phone? Online? I read on The Points Guy blog that it's best to ask in person > then social media > then phone > then online form. Everyone I spoke w/ at the airport (Sky Club and Help Desk) just referred me to the online form.

Thank you in advance for your advice.