I have done a short stretch of a parallel route that goes from Venice to Po via Padova, Monselice, Carceri d'Este, Badia Polesine, Moglia/Sermide last year. it's called via romea leona. this is the website:
http://www.amicidisantiago.it/romea/leona.htm
the walking is flat, often along canals. there were yellow arrows, although I don't remember them very much because I was following my description. there is some pilgrim accommodation. there are shops (or at least a bakery) and restaurants in all towns with accommodation.
you reach the route by leaving venice on a boat to Fusina.
by that route (then crossing down to via francigena across the appenines and following the coast north to france, I needed 5 months from slovenia to santiago)
Venice/Fusina - Padova, 36km (can be broken in two by staying in Dolo, hotel €40-45)
abbazia s giustina, 049/855 0411, 822 0431, you must get foresterario padre Filippo Resta otherwise you can't stay (try calling 4 days ahead), all year, donativo
ostello citta di padova, 049/875 2219, a bit north of old centre, all year (from 15h30), BB €19-23
Padova - Monselice, 22.7km (or 1km further if staying in monasterio s giacomo)
venetian hostel, 0429/783 125, all year, bed €22-35
monasterio s giacomo, 328/343 8580 (call, no sms), all year, donativo
Monselice - Carceri d'Este, 17.5km
abbazia de Carceri, 0429/619 777, no shower but kitchen, sleeping bag & mattress necessary, friendly, call 2-3 days ahead, all year, donativo
stock in este.
Carceri d'Este - Badia Polesine, 22.5km
hotel antonio, 0425/520 36, all year, bed €31
a couple of BBs or ask at the tourist office (9h-12h30+16h-19h)
if calling centro parrochiale, 0425/514 74 - I was accommodated about 2km south in Salvaterra in an empty parish, cold shower and a stove but no bed or mattress
Badia Polesine - Sermide/Moglia on the Po, 33km
centro sportivo in Moglia, attended by parrochia, the phone I got was not working
BB agriturismo Corte Giardina, 338/766 8558, about 1-1.5km S of Moglia, dinner €23, BB €30
in Sermide is a hotel, 0535/610 86
I've also done Torino - the French border bit in 2009, with the help of extremely friendly association that manages that part:
http://www.moncalieriincammino.it/. the kms are approximate, all info and prices are for 2009!
it was not yet fully waymarked in 2009 but I am sure this had changed since then.
by that route I needed 3 monts and 3 weeks from torino to santiago.
Torino - Rivoli, 30km
ostello torino, 011/660 2939, on the E side of the river, dinner, closed january15 - december20, BB €15-22
plus some more hostels, one on the N side of torino near the route, I think
ostello rivoli, on top of the town after the museum of modern art, opens 15h, HP €28
Rivoli - Sant'Ambrogio, 35km(?)
parrochia, 011/939 132 and BB Faro di Nord-Ovest, 339/128 8686, €40
I slept on top in sacra di san michele which is a 1h30 climb from Sant'Ambrogio, arranged by the above association, donativo
stock in avigliana.
Sant'Ambrogio - Bussoleno, 27km
hotel kamal kafe, 0122/493 80, bed €30, HP €45
hotel isolabella, 0122/641 612, HP €45-65
stock in antonino di susa, there are restaurants attached to the hotels.
Bussoleno - Chiomonte, 20km
Meisun Brodel, 347/400 6585, very friendly, dinner €15, january-march + june15-september + november-december, BB €25
stock in susa, although there are a shop and restaurants.
Chiomonte - Oulx, 22km
BB Seguret, 0122/831 164, near the train station, very friendly, kitchen, BB €40
two more BBs
shops are in the centre, stock before going to BB Seguret
Oulx - Monginevra/Montgenevre, 24km
gite d'etape azalee, 0492/218 252, all year, BB €25, HP €40
also various chambres d'hotes (BBs) and hotels
there is a bakery.
