Hill climb riding position
I assume you have worked out the problem is your center of gravity is too far back, so there is not enough weight on the front wheel. This is a common problem, and I have found my new bike is worse than any other I have ridden- I went for a smallish frame for tight technical single track.  I am still playing around to see what I can do. 

I assume you have tried leading forward and getting you weight further forward.... On the track, try to slide forward to the front of the seat. Change down to a lower gear and higher cadence, you generate a smoother action and have more control over the torque lifting the front wheel. 

Ultimate solution is usually a larger frame - more precisely, a longer wheelbase. Assuming you are not able to change you bike there are a couple of things you can do at no or low cost.

Slide you seat forward on the rails - this moves your weight forward, but shortens the cockpit. Get a longer seat, which gives you options of riding positions. Forward for hill climb, back for a a bigger cockpit and better fit. 

Try a longer stem - 75mm is quite short and you should be able to go out to about 120mm. What I suggest is try several sizes and see if you can find a fit that works - talk to your LBS, they may be prepared to let you try on and swap it if it does not work. It's such a trivial job I have seen it done on the trail. Remember to play with seats rails as well. 

Handlebar height. If you have packers on the steerer, lower the height of the bars by putting the packers on the top or the stem, and see how that feels.

As said, all these things are aimed at moving weight forward. Some will change the way you sit and ride, and the best position will need to be a compromise between uphill climbs and other riding. Often, by the time it is steep enough to be a problem, you are quicker to get off the bike.