Soweit wir es einschätzen können, ist die Erfolgschance gut.

Here soweit means something like as far as, insofar as, or more naturally in English, as far as we can tell/judge.

So:

• Soweit wir es einschätzen können = As far as we can assess it / As far as we can tell

It introduces a limitation: the speaker is saying, based on what we are able to judge right now.

Yes.

• soweit as one word is often used in more abstract meanings like insofar as, as far as, to the extent that
• so weit as two words is more often literal, for distance or degree, like that far

Examples:

• Soweit ich weiß, ... = As far as I know, ...
• Es ist nicht so weit. = It isn’t that far.

In your sentence, soweit is the correct form.

Because Soweit wir es einschätzen können is a subordinate clause, and in German subordinate clauses are normally separated from the main clause by a comma.

So the structure is:

• subordinate clause: Soweit wir es einschätzen können
• main clause: ist die Erfolgschance gut

This is very standard German punctuation.

Because soweit introduces a subordinate clause, and in German subordinate clauses the verb goes to the end.

That is why you get:

• wir es einschätzen können

instead of the main-clause order:

• wir können es einschätzen

So the same words would look like this in a main clause:

• Wir können es einschätzen.

But after soweit, the verb cluster moves to the end:

• Soweit wir es einschätzen können, ...

Because German main clauses follow the verb-second rule.

The first position is already occupied by the whole subordinate clause:

• Soweit wir es einschätzen können

So the finite verb of the main clause must come next:

• ist

That gives:

• Soweit wir es einschätzen können, ist die Erfolgschance gut.

If you started directly with the subject, with no opening subordinate clause, you would say:

• Die Erfolgschance ist gut.

Here es is a general object pronoun meaning something like it or the matter/the situation.

It does not have to point very precisely to one noun. In this sentence it means roughly:

• as far as we can assess it
• in other words, as far as we can judge the situation / the chances

German often uses es this way when the object is understood from context.

So you should not worry too much about finding one exact English word for it. It is just the thing being assessed.

It is accusative.

That is because einschätzen takes a direct object:

• etwas einschätzen = to assess something

So in the clause:

• wir = subject
• es = accusative object
• einschätzen können = verb phrase

Yes. einschätzen is a separable verb.

That means:

• infinitive: einschätzen
• main clause: Wir schätzen es ein.
• with a modal: Wir können es einschätzen.
• past participle: eingeschätzt

In your sentence, it stays together because it is in the infinitive at the end of the clause:

• einschätzen können

That is normal for separable verbs when they appear as infinitives.

Because in subordinate clauses with a modal verb, German usually puts the infinitive of the main verb before the modal infinitive at the end.

So:

• wir es einschätzen können

This is the usual order.

Compare:

• main clause: Wir können es einschätzen.
• subordinate clause: ..., weil wir es einschätzen können.

The singular is natural here.

• die Erfolgschance = the chance of success
• die Erfolgschancen = the chances of success

German can use either singular or plural depending on style and emphasis.

The singular sounds a bit like talking about the overall prospect of success as one thing.
The plural can sound a bit more like the odds or the chances in English.

So these are all possible, depending on context:

• Die Erfolgschance ist gut.
• Die Erfolgschancen sind gut.
• Die Chancen auf Erfolg sind gut.

It is a compound noun:

• Erfolg = success
• Chance = chance

So Erfolgschance literally means success chance, or more naturally in English, chance of success.

German forms these compounds very freely, so this is a normal and understandable word.

You may also see similar expressions such as:

• Erfolgsaussichten = prospects of success
• Chancen auf Erfolg = chances of success

Yes, it is understandable and natural enough in German, even though English would often prefer something like:

• The chances of success are good
• The outlook for success is good

German often uses gut with nouns like Chance, Aussicht, or Möglichkeit to mean favorable.

That said, depending on style, Germans might also say:

• Die Erfolgsaussichten sind gut.
• Die Chancen auf Erfolg stehen gut.
• Die Erfolgschancen sind gut.

So your sentence is fine, but it is not the only natural way to express the idea.

It sounds neutral to somewhat formal.

It is the kind of phrase you might hear in:

• reports
• interviews
• business or official communication
• careful statements where the speaker does not want to sound too certain

It makes the statement more cautious. The speaker is not saying this is definitely true, but rather:

• this is our judgment based on what we currently know

Similar German phrases include:

• Soweit wir das beurteilen können, ...
• Nach unserem derzeitigen Kenntnisstand, ...
• So wie wir die Lage einschätzen, ...