This is a very subjective area. I was concerned about this in our own application as there were lots of red flag issues: my prior refusal, the fact my spouse's parents did not know about me, that we are 18.5 years apart age-wise, and there's a significant difference in income. I tried to pick a reasonable number of photographs that would demonstrate that our relationship was genuine. In addition to wedding and vacation pictures together I also picked photographs of ordinary life - like one of my dog (whom I've had since he was a puppy back in 2006) sleeping in my spouse's lap. We had other evidence, including communications between us before my first application was even submitted (e-mail and chat logs).
So it is subjective: you need to look at the evidence and ask how it will be observed by an impartial observer. If you think 300+ pictures are what it takes, then that's the right number to submit.
Using the spouse's last name is actually not considered by CIC. It cannot be, as it is not permitted in some Canadian provinces (Quebec) as a general rule. Couples routinely do not change their surnames (we didn't) and it should have no bearing on the application.
If you are applying inland, you must be living together. That's a statutory requirement of the class. I saw a refusal recently in which both people were in Canada, they just weren't living together (work issues). They were refused because the applicant wasn't living with the sponsor. If they had applied outland, they'd have finished before they were even refused for inland.
Good luck!
