I can’t decide on the name for my son

You haven't commented on Milo. I have no idea if that is a Slavic name. However that is an unusual and excellent Italian name. I only know one. So unusual that it's timeless.
Alexander here in italy will become Alessandro no doubt, and his nickname will be "Ale" unless you keep his real name a secret and always call him Sasha. There are a million Alessandro's in Italy.
There is the name Nicola in Italy and it is firmly a boy's name. This is a good option that you could do with the letter l to make it more Slavic. It will be misspelt by italians but you just have to say "sono Nicola con la kappa invece della ci" and they'll understand. I will warn you that all the Nicola's I know are 30/40.
Modern names to consider here: Tomaso (Tommy), Diego, Ettore, Achille, Matteo, Luca, Alessandro, Daniel (and Daniele), Michele.

Victor is very easy for an Italian to pronounce as the spelling matches the pronunciation and it's a name they know. All the others have letters they'll mispronounce. I wouldn't worry about being modern as that changes and you can think you're doing something modern and then it ages badly. I'm English living in Italy for 11 years. I can certainly help you with perceptions of the names. Victor is definitely a good one though.

This is a name of a friend of mine, I'm not sure what the nationality is perhaps Polish?
Kazamier, his nickname is Kaz, which I think is nice as a casual version of the name.

Another vote for Sasha! I think it's so lovely, I couldn't use it because it's used for girls where I live but I think it's such a lovely name for a boy.

🤣 I think that’s just the way your mind works tbh…

In English a “Maxim” is a phrase expressing a general truth - it’s a well known noun before anything else, unless it has a meaning I’m unaware of in other countries? I know about the old men’s magazine but that’s not published in the UK anymore.

OP I think Maxim is a lovely name - it’s popular in Slavic counties but also in French speaking ones too (although generally spelt Maxime in those) , whilst also being well known in English speaking ones thanks to the classic novel “Rebecca”.

I do really love Alexander too though - very timeless, international, lots of diminutives etc. Perhaps not as interesting as Maxim as everyone knows at least a few Alexander’s, but definitely a can’t-go-wrong sort of name with great historical namesakes too.

Nothing wrong with Victor or Phillip either - but Ian is considered a bit dated now, outside of Scotland where you still meet the occasional young one.

Absolutely love Alexander, maxim and Victor!

I really like Mikhail- Misha and Aleksander - Sasha. Also Alexey, but I guess not so modern and harder to pronounce.

My eldest daughter is called Aleksandra, Sasha for short. We live in England (originally from Eastern Europe) and upon naming her I did not realise that those two names are in fact two different names in UK. The problem I have now- she( daughter) has already informed me that she is legally changing her name to Sasha once she is eighteen as hates name Aleksandra and is known as Sasha. 🤷‍♀️

Us that list I would definitely go for Maxim. I love that name.

I’m surprised there’s no love for Victor. It’s a strong name, and you could start a trend with it!

My son is called Michael but everyone he knows calls him Mischa. It started as a baby name and we expected he would be Michael by the time he starts school but it sort of stuck with him.

He gets a lot of compliment from random strangers on how nice his name sounds ☺️

(There was indeed a lot of confusion amongst the family whether we had a boy or a girl with a name like that but we couldn't care less)

I love Sasha.

I like Maxim from suggestions others have made.

It's Артём? Didn't realise. Every day is a school day!

Alexander is my favourite

I really dislike Ian and Philip

What about Hugo?

Ludo/Ludovic

What about Artem?

I love Alexander / sasha

You can't use Nickolai if your dd is Nikita.

Georgii is good too

Maxim is the name of the main male character in a very famous book, Rebecca by Daphne du Maurier, yet you really hear it used (I think possibly short for Maximillian). My favourite of your list would be Alexander/Sacha because I love Sacha as a shortening, but Maxim is very very good, a very strong name. It also has a meaning in English 'Maxim: a short statement of a general truth, principle, or rule for behaviour.'

I know a German Alexander, nickname Sascha. I really like it. Plus there's lots of possibilities apart from Sascha like Xander or Alex or Alexei even.

Love Alexander nn Sasha . Also Mikhail nn Misha

Im not keen on Alexander but love SASHA as a name in its own right. Also love Nikolai but maybe to similar to Nikita!

Georgii love it.❤

Maxim is my favourite! Or Nikolai.

Sasha and Misha I would assume were girls names if I heard them out of context.