Keep doing what your doing. Sex drive can be a funny thing and it will cycle up and down either on gear or off. Deca is very missunderstood and has this unjustified bad rap. That ratio of test and deca is fine. Deca when taken with test will not cause those problems, its when you come off gear and have no hormones whatsoever except estrogen that lingering deca will cause problems with libido. And even then deca gets too much of the blame.....who the hell would have a good sex drive with no test in system either natural or exogenous and just a bunch of estrogen floating around?
Run the cycle 20 weeks, stop the deca at 16 weeks or so and follow with a solid pct. You should be fine, im the same age and face it recovery may be a little slower and you may not have the drive of an 18 YO