Timaeus ex Mercer

This character has 11 points of non-house virtues and doe not have the house virtue for mercere- switching from affinity with muto to puissant muto would resolve this.

The character is part of the MILVI ANTIQUITI, pg 108 of HoH:TL, where it says they can have Mutantum Magic as their Free House Virtue.

since a donkey is perceived as a stubborn animal, would a Rego Animal be appropriate Technique-form combination to bind one as a familiar? if not, what Technique would you find acceptable?

In my copy of True Lineages p.108 is the beginning of flaws for mercere house characters, and does not describe any such tradition.
Th Milvi Antiquiti is on p. 98.
If you are going to rely on such rules you should note them in some way on the character sheet- mark Mutantes as your free virtue, mention the societae within the background text, etc. I have not memorized the 30+ books I use for reference and expecting these things to be simply recalled based on an assumption is not reasonable.

Am sorry, will keep that in mind, though it is listed as the Free House Virtue in the table

Your spells have issues- the last three are listed as being InAu despite this not fitting the names at all, your wizards communion is at level 20 despite the fact that you would only be able to learn MuVi spells up to 18. I haven't looked them all up yet to verify them beyond these points...

I adjusted the last three spells to their correct level, form and technique.
Wizard's Communion is level 20 simply because of the Mercurian magic Virtue, which says that you get a free Wizard's Communion at the same level as your highest Ritual spell, for free. And every time you invent or learn a higher level Ritual spell, you get a free Wizard's Communion of that same level. And yes, it does mean that he will learn Vim more, so he can actually cast the Wizard's Communion with little worry.

None of your spells are rituals

Binding the Hermetic Codex is a Ritual.
Covenants pg 97

The word ritual appears in the description but it is not defined as a ritual spell nor is there any reason for it to be one.

Ok. Then I will remove Wizard's Communion

Removed Wizard's Communion

The character as it currently stands has 10 points too many if this is at gauntlet. Given the assortment of abilities I'm not going to worry about this, just be aware that your first 10 points post gauntlet have already been spent.

I had to redo the math, and you were correct, I wrote 50 for Latin 4, when because of Linguist it should be only 40 for Latin 4. That's the extra 10. I adjusted the XP spent on Latin to 40. My bad.

I plan to make him a few years past his Gauntlet, but figured it best to first make sure he's good to go as just past his Gauntlet, as it's easier to calculate.

Taking him past his gauntlet, I don't suppose he had time to settle into Acre, and set up his Lab there in the intervening years, right?

That would be fine.

regarding the lab- you will set up the equipment, there are some virtues that are available depending on what magus originally designed the space- auspicious shape, studio, and gallery may be taken but are mutually exclusive, size may range from 0-2, well insulated, elevated or grand entrance, superior construction. There is one lab which is diminutive, which has the studio and grand entrance options (originally created/occupied for a small verditius).

Might I be allowed to have a Size 2, Superior Constructed, Well Insulated and a Studio?
If that's too much, i can ditch the Studio. (It is gonna be a library, for him, so making it safe and well insulated are his primary priorities.

That would be fine.

any idea where you would have a donkey template to start your magical animal companion?