starting a smurf will not help. if you improve, your rank will go up. It goes up by essentially the same about if you have 30 games or 3000.
It's not like an average where the more you have the less any more will be able to affect it.
if you are gaining about the same for a win that you lose for loss that's normal. It means that your MMR is about where it should be for silver 5.
In other words, you are a silver 5 ranking with a matching silver 5 MMR.
The problem is that in order to move up, you have to win more than you lose in silver 5. - and really why would it be any different?
if you are silver 5 and winning 50% , then you are at a silver 5 skill level and will stay at that rank until you win more than you lose.
Suppose you played on a friends account who was bronze 5; I fully suspect that you would immediately win enough games to start progressing from bronze 5.
Now if you had a gold 5 skill level, you would do the same in silver 5. You would win games like crazy.
In fact, in season 6 I was gold 5 and when i started playing on an old silver 5 smurf, i won about 75% of my games.
The same is not usually true when smurfing plat to gold (I am plat 5 now)