pugnatum est = the battle was fought. This use of the so-called impersonal passive is very frequent, and is generally best translated by taking the root-idea of the verb as a subject.
et ubique atrociter = and everywhere fiercely.
Ib 2. circa consulem tamen = around the consul however.
acrior infestiorque pugna est = the battle is more keen and more vehement. This presents no difficulty; acrior and infestior must qualify pugna, which follows immediately.
IIa 3. eum = him, plainly consulem (i.e. Flaminius), for no one else has been mentioned. Notice the emphatic position of eum.
et robora virorum sequebantur = both the strongest of his troops followed. You may know that robur (lit. hard wood) is often used of the toughest troops, the flower of an army.
et ipse = and himself, i.e. the consul (Flaminius).
3-4. quacunque in parte = in whatever part.
4. premi ac laborare senserat suos = he had seen his men hard pressed and in distress. No other meaning is possible, nor does the order present any difficulty, but notice the emphatic position of suos.
4-5. impigre ferebat opem = actively he bore help.