Syrian government controls alot more territory than people are mentioning, around 80%.
All the red and orange is directly under Syrian government control, the Yellow one is under Kurdish rebels but the Syrian army is also using the same area. The green are under the control of Turkey and white under terrorists. I dont understand why Turkey is backing the white area terrorists, they are clearly takfiris. The only reason it's a statlemate because of Turkey as they have their army there.
Regarding Iranian air defence systems for Syria. Bavar-373 and 3rd Khordad long range SAM would suit Syria, they need to buy it ASAP, the issue is their effectiness is a question mark and Syrian army is untrustworthy, as so many soldiers changed sides during the civil war.
Iran is openly talking about upgrading Syrian air defenses to help Damascus fend off continued Israeli airstrikes.
Iran is always making big statements but never delivering it. Just do it. Does usa make big noise before arming Israel?
Syria also has T-90As main battle tanks. Will need alot more to build their army again.