To use the syringe: select the syringe, hover over her breast or pussy area, hold click so it zooms in, click middle click and wait as the injection goes into her. If you click there will be a white flash on the screen but I dont think it does anything since it's not listed in the controls.Still can't penetrate her in my own save. I also still can't figure out how to use the injections. The screen flashes white when I press like I would to use the drinks, but no decrease on the bar in my inventory and no movement from the syringe in my hand. I bet it would help get beyond 4x if its effect in previous games is any indication.
Make sure to use the Adult (tier 3) injections since those are the ones that increase her sensitivty.
The stats move very slowly for me as well, I don't really pay attention to them. Even though my numbers are low its very easy for me to penetrate her now. Anal is at 36 and anal expansion is at 78 and I can shove it in without any foreplay. Not sure if it's bugged or if it's supposed to be low because it totals up all the related spots (Anal + Inside anal + deep anal).Did v1.03 actually fix the expansion stats bug? I downloaded it and started a new game but so far I'm finding it impossible to do anal or urethra sex, whereas with v1.00 I was able to. The stats don't seem to budge no matter how much I finger her or stick the drinks in her. Ditto with her sensitivity stats -- I can attach the rotors to her nipples and grope her breasts for ten minutes and have her cum 100 times from it but the stats only move up by a point afterward.
The way I increase her sensitivity (and make it easier to penetrate): Use your tool and click/rub the areas you want to increase the sensitivity on. Once the "damage" reduces to a small number (<10 or so) use an adult injection or splatter the adult drinks on the area you're working on to reset and increase the damage done. Then repeat, making sure to use the drinks and injections to keep her stamina above 0. You can use your penis/sex toys on auto while you're doing this to attack more areas at once. It shouldn't be long before you can easily penetrate. I do like 2-3 sessions of it.
I haven't figured out how to get the broken heart yet, I tried smacking her a ton during sex and making her climax while shes knocked out but neither did anything.