As usual, a lot of misinformation had been dispensed. For one, changing only the stem length and nothing else has very little effect on weight balance. Anyone who really wants to see how weight balance is changed only needs to set a bike onto a trainer with a scale under the front wheel. If you only move your hands back, like a shorter stem would, there will be every little change to the weight on the front wheel.

The two things that have the greatest effect on weight balance are saddle fore/aft position and torso angle. With that scale under the front wheel, start with your hands in the hooks and upper back nearly horizontal and note the weight. Then slowly raise the torso and watch the weight drop.

Without some specific body dimensions from the OP, it would be difficult to make any recommendations, but I do have one test for adequate stem length that anyone can try. When riding in the hooks, with the fingers in reach of the brake levers and the upper back nearly hoizontal, any small amount of knee to arm clearance indicates adequate stem length. A lot of knee to arm interference means your stem is short. Of course you can always flare you elbows to eliminate the interference, but at least it tells you where you stand with regard to stem length. If you have a small amount of saddle to bar drop, then that low back position will require a lot of bend in elbows, that creates knee to arm interference. If you have an 8-12cm drop, then the arms require little to no bend and there's less chance of knee to arm interference.

I've got a short torso, at 5'-6" or 168cm tall with an 83cm cycling inseam and 73.5cm saddle height. One of the ways I manage to use a "normal" 110mm stem length is with the aid of short reach bars and Campy brake/shift levers. Using normal 85mm reach bars and Shimano brake/shift levers would require a 15-20mm shorter stem. It also helps to be flexible and have good core strength.

I suspect that part of the OP's problem is a lack of fitness that makes a low torso angle uncomfortable, but the problem can also be a saddle that is too far forward. With the proper weight balance, their will be very little weight on the hands and both more reach and drop can be tolerated.

A mistake often made when comparing frames is only looking at the TT length and ignoring the seat tube angle. Steeper STAs lenghten the frame reach, for a given saddle position relative to the center of the BB. The average amount is about 1cm per degree.

I would never make a huge change from a 110mm to a 70mm stem. Even a change to a 90mm is quite large. I'd check the saddle fore/aft position first. A saddle set to produce KOP is often too far forward.

With regard to the recommended frame size, keep in mind that the ST length has no effect on the fit. What you really need to look at is the head tube length, with the headset to determine the true vertical size of the frame. There are a lot of brands that have frames with extended head tubes for the more recreational rider. Those frames can help to produce a taller handelbar height, but if you want the bars only a few centimeters lower than the saddle, that almost always requires a high rise stem. A 73 degree stem, flipped to a 107 (+17) degree angle will raise the bars by about 6cm, but if will also result in a stem length that is about two sizes shorter (horizontally). Also looks goofy, but whatever it takes.