1) .5 deca and .5 test doesnt tell us enough. .5mL of 100mg/L is obviously way different than the same volume of 300mg/mL. Here guys will tell you cycles in mg/week so you need to know concentration. Im assuming you have test cyp or enanth.
2) I would guess most guys here would say that you should start out at 250-350mg/wk of Test. No need to go higher. You can learn a ton about how AAS work for you should make great gains assuming your diet and training is on point. Plus you keep sides to a minimum. Nobody can say what you will gain, but personally I think 8-10 lbs is a very reasonable goal.
3) AAS obviously help you recover faster so you would think it would make sense to start while you are hurting so you will recover. Others may disagree, but if it were me, I would make sure I was fully recovered first. You are about to push your body harder than you ever have. Muscles will grow but the tendons seem to lag behind and it would suck to know that you arent fully taking advantage of a cycle (or you have to cut it short) because of tendonitis. Im sure that others will chime in and perhaps they will recommend a SARMs healing stack to get you ready.
4) I would strongly consider doing precycle bloodwork so you have a baseline of where you are. They are cheap through a place like
http://www.privatemdlabs.com/...........around $60 after discount code to get your total test, E2, LH, FSH, and a few others.
With that, Ill leave it to some others to chime in with some full cycle layouts, PCT, and/or questions, info, etc.