Doudle URLs without Canonical link and a change in keyword.: What are the effects on SEO?

[trevordocs]

I built my new website and i have two major worries.

1. My home page has two URLs. The one with a high PA though indexed by Google, is not submitted in the sitemap. I tried to place a canonical tag but the hosting service said it was impossible for me to place the canonical link. My concern is if the indexed page will be successfully optimized for SEO without it being submitted in the sitemap and what happens to the other URL for the same page which is also indexed and submitted in the sitemap?

2.I started my link building campaign for one of my pages. I acquired some good PA already for a particular keyword  but later on discovered it will be very difficult for me to rank for the major keyword. I have decided to change the keyword. Will the acquired PA influence the SEO for the new keyword? I wish to know if i should dissolve the links to the page for the former keyword or should i maintain them and move forward with building links for the new keyword as well.