welcome to the boards
my thoughts on your questions
1) people on this forum do use a EQ5 for a similar telescope, but i dont think you will ever be annoyed you spent the extra money on a mount. the more weight capacity the more stable your scope and the better the subs you are likely to get
2) if you are looking to get into astrophotography, a autoguider is the best use of any additional money
3) Nah, i have had my 10" and eq6 in the back of a hatch, the scope usually goes across the back seat