Actually, Ludovicus is right, if the dog is 'known'...but if it's a strange dog (not known to the people), then it would probably be your solution. Sounds horribly confusing, I know; but direct objects which are people receive the 'a'--and when 'a' and 'el' are next to each other, they're contracted to 'al'--but often times tamed animals, particularly dogs and cats, are included in the mix. That's about as clear a description as I can give.
In many times, yes. Same with Spanish, depending on the clefting involved.
Ludovicus: depends on which tense of the subjunctive you're talking about. Present subjunctive is no contest: it was passed onto the Romance languages as-is, and in fact is one of the few verbal constructions where the inflection and the semantics behind it remained just about the same. As for what the modern languages used for the past subjunctive, that varies: Italian derives its past subjunctive from the Latin pluperfect subjunctive, and Spanish has/had competing forms deriving from the Latin perfect subjunctive (which is really the one what has won out) and the Latin pluperfect subjunctive (which has seen significantly decreased use since the 19th century, at least).
As for your word-order examples: it really depends on what it is you're saying. Yes, it's possible to have all of those orders in Spanish, and I believe that they are also possible in Italian. But it really depends on what the discourse functions are in the conversation--what the topic of discussion is, which party has already been introduced in the discourse, and what the context of the discourse is. Furthermore, I would argue that Al perro Maria ve and Maria al perro ve are highly marked, and would not occur; I would mark them as questionable at best.
Bottom line: I wouldn't say that any of the modern Romance languages are 'close' to Latin in terms of syntax, because there have been such leaps in terms of word order, nominal and verbal inflection, roles of function words, and clause construction.