I would say that you are on the right track with your plan.
The 33lb Rocna
or 35lb manson would certainly be large enough for your boat
even with the relatively severe weather
it sounds like you get. Having multiple anchors is always a good idea so maybe the Bruce could become your second anchor? The new generation anchors truly are a lot better and will make you feel much more at ease.
Do you have a windlass
? If not, 75' of chain will be a real chore. If you don't need the chain for abrasion resistance, you might think of going to something like 50' or even 40'. In addition, the chain will be adding a lot of weight to the bow of your boat which you want to avoid as much as possible. I would go with 5/16HT, the rest of your system will be capable of exceeding the working load limit of 5/16" BBB chain pretty easily. The shackle is important as well and something like a load rated 3/8" Crosby would be wise.
The line is definitely on the light side. It is by far the most prone to chafe of any part of your system so it needs to be a bit oversized. If it were me, I would be using 5/8". 3 strand is fine although many people now prefer the fancier rodes such as anchorplait or 8 plait. They do stow better and are easier to handle but they are more expensive. A piece of tubular webbing to use as chafe gear
would be good as well.
For comparison, on my 30' 10000lb boat, I use a Rocna 15 (33lb), 30' of 3/8" chain (not ideal but I had it lying around) and 250' of 5/8" 3 strand. While my boat is slightly heavier, it sits extremely well to an anchor so doesn't shock load the system very much.