I doubt any good hotel is there in Jungshahi. There will be sirai or charpai type of hotels if any.
The best you can get in Jungshahi is Pakistan Railways Dak Bungalow but for that you will need a good contact in Pakistan Railways.
And yes you will find transport for Thatta for sure from Junghsahi. However, there is another option of train from Jungshahi to karachi. Currently you can catch two trains Bolan Mail & Zikria Express which have stops at Jungshahi.