Solutions.:
1. If you don't know how to use a linux distribution virtual private server, which is the best one to choose, learn how to, instead of using windows.
2. For a small server like you've told me 15-50 you must get a virtual private server with at least 4GB ram, 4 vCore @ 2.27GHz, 1 GBPS bandwitdth, and at least 80GB+ HD, that all will be enough to hold at least 300 players without laggy if your server network is written correctly.
3. Do not use TrentaHost, their web hosting and virtual private servers are outdated and full of vulnerabilities.
Answers.:
1. If you have sure that'll stay just in this player base of 15-50 so 2GB ram are enough, but if you have faulth in getting bigger soon, so go for 4GB.
2. You must use Eclipse with Jrebel so after each update you doesn't need to restart it, that'll be better for the community because you will not interrupt their gameplay.
3. Depends on your server network system and stability man, but if you want it to run smoothly at least 2GB.
If you have any other questions private message me your skype.
https://sitespace.io/vps/ - VPS 4 - $ 20.00/monthly (a good one)