Advice on anchor / Stern anchor line please

Hi,
We are planning a spring cruise in a northern isolated, windy area with strong currents (beautiful though ). I want to ensure that our anchor lines are adequate. We have been using a 1/2" three strand nylon anchor line with 20 feet of chain, usually anchoring in about 30 feet depth with a Bruce anchor. When necessary we use a 5/16" polypropylene stern line to tie to shore.
Our E30+ weighs 9,000 lbs.
I've tried to check breaking strength for these lines, but what I don't know is how much pressure or weight is applied to our boat in various wind strengths.
I have been anchored with our current lines in 30 knot winds, and they held. Does anyone have any helpful information on how many pounds of pressure our boats experience in various wind strengths? I'm most doubtful about our stern line, but it's been good so far. But we obviously need to ensure that our main anchor line is also adequate.
Thanks for any help on this.
Frank

We used 5/8" three strand for our rode on our 38, so I would be quite comfortable with 1/2" for your 30. But I would up your polypropylene line when tying to shore, especially since you can sometimes develop pretty strong forces with a beam wind when tied to shore. If that does ever happen to you, remember that you can significantly lessen the load by letting out enough extra front rode and stern line to reduce the line angles from ~180° to ~120°.