The Gladius is not like the DTA SRS Covert so you're not going to have an issue with the scope objective being right next to the end of the barrel. Since you want medium to long range shooting with possible hunting at some point (why not, I'd take that rifle hunting any day!) then might I suggest the Vortex AMG 6-24x50, even though it's low end is 6x it actually has greater FOV than the NXS 5.5-22 you were looking at. The AMG is a solid scope that I think would work well for you. I admit the aesthetics of the Ultra Short scopes are appealing especially on short rifles, take a look at this thread for more information -
https://www.snipershide.com/shooting/threads/2018-year-of-the-ultra-shorts.6868822/ If your price range is around $2k then most of these are going to be outside your budget except for the EOTech Vudu 5-25x50 at only 11.2" or the Leupold Mark 5HD 3.6-18x44 at 12", but both of these are unproven scopes as they have not gone into production yet, the only ones in production are the Sig Tango 6 3-18 and 4-24 which are a little hefty but nice and short. Also, keep your eye out on the classifieds as they have some great deals, I have seen Tangent Theta's TT315M for under $2500 which is an absolutely killer dealer, you will not find better optics than this. I've owned two Premier LT 3-15x50 (the TT's sister) and miss those scopes greatly. That being said, the PST II 5-25x50 is a solid scope (I own one) for the price, is it going to be NF quality, no, but you're not paying for that either. In comparison to my other alpha class scopes, the PST II is a great package for its price. If you want a little better glass but don't want to pay much more then look at the Bushnell ET LRTSi 4.5-18x44 scopes, they are pretty amazing as well, Bushnell's DMR II is another great scope but doesn't have as good of glass as the LRTS, but their recently announced DMR II Pro with upgraded ED Prime glass should resolve some of the issues of the DMR II.
A few years ago there might have only been a few scopes to recommend; however, there are so many options now it is both a blessing and a curse, a blessing because there are some amazing new optics to be had at great prices, but a curse because there are so many options how do you choose. I'd suggest finding a reticle you like and going from there, as long as you buy a "good" scope then I think you'll be pretty happy and you can always sell a good scope in the classifieds to upgrade down the road.
