I've spent wonderful time, including 3 consecutive nights of NL action. The weather didn't cooperate with us in Jokulsarlon over 4 nights. No sunrise / sunset or NL during the visit. Because of that I felt I missed out on the opportunities in the area and want to revisit for a longer trip. I think 3 weeks will be enough to cover the whole country. I already got a feel of the area from Reykjavik to Hofn (on Route 1) and want to explore the rest of the country. Being in the country for extended period of time I can move around according to the weather and get the most out of it.
What I need help is the following things around Route 1:
1) Any areas on Route 1 you recommend as place to crash for the night. Something that can be used for sunset & sunrise or within close distance to opportunities
2) Any public hot springs along Route 1 that I can use for shower facilities. Anything will be helpful and I can map things along the way in advance based on recommendations.
3) Same applies to hostels / guesthouses / motels. I think staying in a real bed at some points of the trip will be necessary.
4) Any and all landscape / macro / abstract photography opportunities along Route 1 I should explore
5) Any glacier walks & ice caves I can explore
I am also looking for general guidance with other aspects of the trip. Since I am there for so long I guess it would make sense for me to get a cell phone. Any recommendation on something that is prepaid and will get good reception along Route 1? Any good restaurant recommendations along the way? Any places to get good beer? 
Any kind of input would be appreciated.

. Especially in supermarkets, where the most alcohol a beverage can contain is 2.5°. You have to go to liquor stores for anything stronger.
- $8
