First off I recomend you increase your doses by at least double. As I have said before, if you are going to supress your hpta, you might as well get some good gains out of it.
Also front load your Deca for the first 3 weeks, and your test for the first week.
that means 800 mg of deca for the first 3 weeks and 800 mg of test the first week, then 400 for the remaining weeks on cycle.
As for comming off cycle, you will have to taper your testosterone enanthate unless you want to be shut down hard, libido wise, by the nandrolone decanoate. The following protocol bellow will work just fine.
WK 1-8: Deca/Test 200mg a wk.
Begin tapering off cycle
WK 9: 200mg enanthate
WK 10: 100mg enanthate
WK 11: 100mg enanthate
WK 12: 50mg enanthate
WK 13: 50mg enanthate
You can use nandrolone phenylpropinate instead, which would eliminate the need for the long taper since it has such a short half life.
Use arimidex if you can get it, or femara. If you dose correctly, reduction of gains should not be a problem at all. Elevated estrogen causes increases in water and fat retention, those aren't gains.
Yes, the estrogen will slowly dissipate, but if you are using nolvadex and stop it too soon, there will be a rebound effect, that is why an aromatase inhibitor is a better plan
Your testosterone will return to normal levels, but It will never be as high as it was before your first cycle. Messing with HCG will only make the problem worse. The best thing is to start off with short acting compounds such as orals, and injectables with short chain esters, that clear the body quickly. Avoiding highly androgenic compounds such as test, tren, and deca, and sticking to the lesser androgenic compounds such as anavar, winstrol, primo, e.t.c. will also be better for your libido in the long run, as well as keeping those cycle short - i.e. 6 weeks, clearance included, as the max.
No you should not have any problems with fertility issues if you are taking rests. Example: Hulk Hogan, the man was on the juice for twenty years and has kids.
Store your gear in a dark place at room temperature and it will be fine.