Are you pretty much maintaining your weight on 3500kcal a day? If so, I'd stick with it. You should get a nice recomp effect out of your gear. If you want to get a bit leaner, try reducing your intake once you start taking the Var for leaning out/hardening up in the final weeks. Don't go overboard with the kcal, you'll just end up doing more harm than good with it.
If your current split is working for you as it is, it will work even better on steroids. But to be honest, I've seen a lot of (naturals) doing 5 day splits with insane volume and never getting anywhere. And the worst part was that they deluded themselves into thinking it works (not saying that's the case with you, just a general observation).
Problems with tendons and joints can indeed occur when you make big jumps in working weight. That doesn't mean it has to happen. In fact I'd say it's rather rare, unless you make really, really crazy strength gains (can't quantify really, also again: depends on your prerequisite). Also note that Oxandrolone reportedly helps with tendon/connective tissue recovery.