You do not choose a boarding time. You choose a check in time. Boarding begins around 11:30 and is based on numbers given out when you check in, unless you have a priority.
You need to realize that land based vacations are what you need because you are not going to find any cruise line to come close to your unreasonable expectations.
After having spa passes for my past 6 cruises I have reached the opinion that they are not worth what you pay for them. It takes a lot of time in the spa to justify the cost and on a port intensive cruise like Alaska, it is hard to find the time.
The week prior the rooms were ready around 3. I feel like this is going to be the new normal because of the change to once a day room cleaning with fewer stewards, it simply takes them longer to get the rooms ready.
Are you really considering taking that good camera with your telephoto lens to the beach around all that sand. If you are they you are going on a picture safari, and not a trip to the beach where you will do any beach activities.