I must tell all travelers to Manali that in Manali you will rarely find any Indica running as a local Taxi. The most common small car which is similar to Tata Indica is Maruti Alto, slightly small in cabin space, but more sturdy and reliable for hill roads.
So if you are 2 to 3 persons, I would suggest you to go for it and if the number of persons is higher, then book a bigger vehicle and the rate will also go up accordingly. Please find below the answers for your quries;
a) In local sightseeing I would suggest you to only go for Hadimba Devi temple by transport which is the most beautiful point in this list, you can go there by Auto Rickshaws and you may book them for one way drop only.....and the charges for that should not be more then 70 – 100 Rupees for 3 PAX. On the way back you can walk back through the beautiful Cedar forest towards the Old Manali bridge and from there you can choose go to Old Manali or Club House. And from there it is a very pleasant walk through the forest down to the Mall area of Manali. And I am very sure that you will enjoy the walk a lot. As you will have no restriction of time, while by using a taxi you have to pay extra for waiting hours and most of the taxi drivers try to show you all the points in a hurry and you can’t enjoy the nature of the place. Tibetan Honester is a 5 minutes walk from the market, so you can combine it with your shopping tour, in one of the evenings.
b) On the Solang Valley & Gulaba tour day, you can include the drive up to Vashisth Hot Springs and Temple, Beas River Point (Near the confluence of river Manalsu & Beas on Solang Valley road). Approximate fare by Alto should be around 1250 to 1500 rupees.
c) Skip all the temples mentioned by you in Jagatsukh as you will be disappointed. Go straight to Naggar and visit the Roerich art Gallery (both upper and main lower parts) and check Naggar castle for it’s history and Jagti Pat Temple and a small Pahari Museum and great view of the Beas Valley. If you have time and you like to walk..... a small hike of 40 to 50 minutes one way can take you to beautiful & ancient Krishna temple, Just above the Naggar Castle (you can ask any local for direction). You can also combine excursion to Jana Fall in this tour and am sure you will like it... do not forget to have your lunch at the local Dhaba.... just below the waterfall at Jana.
d) Avoid booking cars through any tout or hotel, walk directly into the office of Himachal Taxi Operators union in the middle of the main market in Manali and book your transport from there on fixed charges.
Hope it helps.