Difficulty and Block rewads

Hello,
I am pretty much new here.
I 'd like to get some feesback about something.
I'm not sure that's really a new topic and I apologize if not.At siamining.com there are some APIs and one of them (https://siamining.com/api/v1/network) sent me some results like that :
{
"block_height": 140871,
"block_reward": 159128,
"hash_rate": 1.017987298999e+16,
"difficulty": "6461570807191862099",
"next_difficulty": "6479331873882250480",
"blocks_to_retarget": 1,
"time_to_retarget": 635
}and later (32 blocks later):
{
"block_height": 140902,
"block_reward": 159097,
"hash_rate": 1.0420477199684e+16,
"difficulty": "6542073748822332437",
"next_difficulty": "6546775100144821087",
"blocks_to_retarget": 1,
"time_to_retarget": 628
}I see that the number of blocks has been increased by 32 and in the same time, the block rewards has been decreased by 32 too.
I made several tests and that's work each time. In that case, there is a limit to the reward of blocks. And if I add the rewards of block to the block height i get 299999 (300000 with block 0).
In other hand the total Hash rate is about 1e+16 Hs (Siamining). If I add 122700 Antminer A3 (what is enormous) at 815 GHs I get 1e+8 GHs = 1e+14 Hs
thus the Total Hash rate becomes 1.01e+16 so it's 1% of increase.
And the difficulty grows up just a little (the same 1%):
If 631s is the time for one block the difficulty is 631 x 1.01e+16 = 6.373e+18 to compare with the previous : 631 x 1e+16 = 6.31e+18Am i right?
If yes the change of rewards is more due to the decrease by 1 SC of the block reward each block mined (about every 631 s) than due to the difficulty.
In a month the decrease of block rewards is about 4156 SC (30.5x24x3600/631) and only because of the decrease of block rewards.
Right now the block rewards is about 159000. If I divide it by 4156 I get about 38 month before 0 SC.
That's a little bit long but i'd to get your thoughts about.
Thanks for those who read that until the end ;)
Eric

Hello,
I made a mistake when i did the calculation... should i stop to drink the cooling water of my computer?
I said:
"In other hand the total Hash rate is about 1e+16 Hs (Siamining). If I add 122700 Antminer A3 (what is enormous) at 815 GHs I get 1e+8 GHs = 1e+14 Hs"That''s completely wrong!
By the way, Hash Rate of Antminer A3 is 815 GHs so it's 815e+9
so if the batch is about 10000 units, the total Hash Rate is pretty much 815e+13 or 0.815e+16
And If I add that batch to the total Hash Rate I get:
Total Hash Rate is about 1e+16 + 0.815e+16 = 1.815e+16 so that increases the total Hash Rate of about 81.5%...
What I said about SC decrease block reward remains true.
So the difficulty have a reel impact on the reward but block reward decrease add a reel negative impact too on the rewards.
We are gonna have at least 3 batches from Bitmain, 2 batches from Obelisk and at least 1 batch from Halong in 2018. I think it's about 5e+16 to add to the total Hash Rate!
The only way to earn money in 2018 when we have a small budget to buy ASIC machine (1 or 2 machines) is to count on the increase of the worth of Siacoin.
And I am wondering whether, in that case, we should just buy Siacoin instead.
Eric